I have been using Kubuntu Hardy for the last few years. It's all right but it's not quite as polished as the hordes of (K)Ubuntu fans would like to believe it is. I was a Mandriva user prior to that and Kubuntu has nothing on Mandriva in terms of polish, though it has community, support, and timely bug fixes (maybe) that Mandriva never has been able to achieve.
Before people jump in with "rpm-based systems suck and Debian-based systems rule", I have no problem with rpm or deb based packages. I administer both Red Hat and derivatives and Debian and derivatives and both have their pros and cons. In fact, in our hosting operation, we run both types of systems and have no major complaints with either. I'm using Fedora on my desktop because of a few interesting projects, Cobbler and FreeIPA being two. If Debian and its derivatives offered anything like this, I would be using one of them. The problems I have encountered have been entirely within user space and have nothing to do with the package manager used by the underlying operating system.
Email is the mission-critical application for most people and I'm no exception. I like using desktop email clients. I don't like using web mail clients, even the much-vaunted Gmail. I occasionally use Mutt when I have no choice but I can't see myself making the time investment that would be necessary to become proficient at it. In fact, Eudora on Windows kept me on Windows for longer than I wanted to be until I gave up on the idea of converting more than 10 years of email in Eudora and just started fresh in 2004 with KMail, which I loved. I'm aware that Eudora "just" uses mbox files and that it "should" be trivial to "convert" to any other standards-based email client but the reality is a bit more complicated. While I could certainly open those mbox files in KMail, I couldn't preserve the meta-data about that mail, such as which I forwarded, which I replied to, etc. and that was important to me. I eventually elected to leave that mail in Eudora and gave up on the idea of converting. I very occasionally have to refer back to that email and just fire up Eudora on Windows XP to look at it.
Fast forward to 2007 when I made another big change in how I handled mail and my world was rocked. I migrated to IMAP from POP because I got tired of being tied to one computer to check and reply to my email. My beloved KMail, unfortunately, didn't make the transition because it was painfully slow in checking IMAP accounts. The benefits of IMAP outweighed the benefits of Kontact/KMail so I switched to Thunderbird. In the process, I lost some things but gained others, not the least being that IMAP Just Worked as one would expect.
Fast forward to a couple of weeks ago when I got a new machine and decided to run Fedora on it and I have quite possibly the worst transition in all so far. Fedora 11 installed Thunderbird 3 Beta. To say it's buggy is an understatement. It's to the point of being unusable. I have extensive filters, particularly for clients. Email from clients are high-priority so they get moved directly to their respective mailboxes, tagged with "Client", and I have client mailboxes, as well as a few others, marked as "Favorite Folders" so that in the "Favorite Folders" view, I can see at-a-glance when I get new mail. Folders with new mail are highlighted with a red font and a count of how many unread messages. Only one problem. Thunderbird 3 wasn't providing any indication that I had new mail in those folders. It was only when people started calling me wondering why I was so unresponsive and asking "Did you get my email?" that I clued in what the problem was. Not good.
I removed Thunderbird 3 and just installed Thunderbird 2 from a tarball. It's pretty self-contained so it's not a big deal that it's no longer under package management. Aside from the UGLY default GTK look, it mostly looked and behaved pretty much as Thunderbird looked and behaved on Kubuntu Hardy. There are some oddities, like these things they call "Smart Folders", which aren't all that smart, but I can live with them and the most annoying one, which I'm finding difficult to tolerate, I sometimes have to save an attachment a few times before it's really saved. I often get zero byte files saved when I do a "Save as..." and yet, if I use Thunderbird on Kubuntu or Windows, it will save it properly the first time, every time. Another annoyance and mystery is why Thunderbird seems to render some, but not all, messages sent as plain-text with an ugly, 5 point Courier font as opposed to the Bitstream Vera Serif that I have set as the default.
Being a Kontact/KMail fan, I tried KMail in KDE 4 with the hopes of going back to it. It's "all growed up now" with all sorts of fancy features but it's has one fatal flaw that keeps me away from it. KMail apparently does not support IMAP IDLE, which means it has to check every folder for new messages. In my case, because I have hundreds of folders, there is constant disk churn while KMail scans every folder, some of them with 40,000+ messages, and the cycle time for doing that check is longer than the mail check interval of 10 minutes. Clearly, that's not feasible.
Though I'm a fairly technical user, I'm lost in the land of Linux audio. I have no idea why the sound sub-system has been changed and I don't care that the current one might even be "better". If it takes half a day of poring over docs, tolerating rude people on IRC, and still having something that doesn't work half as well as the "inferior" KDE 3 sound system worked, then it's not progress. I'm so clueless on this that I'm not even sure whom to blame. All I know is that sound is flaky on my system.
Though I prefer KDE applications, I'm not so religious about it that I won't use GTK/Gnome applications, like XChat. I've been using XChat for years and have tried to like Konversation and Kopete as an IRC client but they have never come close to the stability and functionality of XChat. I copied my .xchat folder to the new machine from the old one and things almost work the way they did in the old machine but the omissions are glaring and have me wanting to go back to the old machine. In the old machine, if someone mentioned my nick in a private chat, the XChat icon in the kicker panel (the taskbar) would be highlighted to get my attention. That doesn't work in KDE 4.3 for some reason. I have no idea why and life is too short to spend hours digging for an answer. I tried Konversation but it still came up wanting. It's still implemented with KDE 3, apparently. I don't recall the specifics but XChat with its warts was still preferable. Same went for Quassel, a KDE 4 IRC client. So, I'm left with less than I had before. This is progress?
In KDE 3, I have many konsole "sessions" saved. It's much more convenient for me to pick from the session menu the name of the machine to which I want to open a session than to remember that I need to forward some ports across the ssh tunnel, etc. I grouped konsole sessions that are represented as different tabs in a konsole window into a thing called a "profile" so that I could click on one icon in a panel to open sessions to all of those machines in one pass rather than have to do them individually. (RSA key based authentication makes all this a snap.)
Konsole has been rewritten for KDE 4. There wasn't any obvious migration path for all those konsole sessions and profiles I had created in KDE 3 so I resigned myself to having to recreate them in KDE 4. I didn't want to do this stupidly by pointing, clicking, filling in forms so I created one profile (yes, what was formerly called a session is now called a profile - thanks, that really clarifies things), and examined the file that was created to see if I could just copy the file and modify the bits in the file that needed to be modified for a new session, er, profile. It seemed pretty straightforward. One problem. I didn't see the new profile that I created with the copy/modify method in the list of profiles in the File menu or in the "Manage Profiles" window. Once I exited konsole completely and relaunched, I saw it in the "Manage Profiles" window but I had to enable them to be shown in the File menu. There were redraw problems and even though the text file containing the profile information explicitly said that the profile should be shown in the File menu, unless I went through the process of clicking on the "Show in Menu" checkbox in the "Manage Profiles" window, they would never show up in the File menu. Let's say that this is an annoyance and a one-time hit that once I've created all the new profiles, I don't have to bother with again. What do I do about these groupings of sessions that I used to have? I don't see any obvious way of opening a konsole window with one tab per profile open. Again, this is a loss, not a gain.
I loved KNewsTicker in KDE 3. I had a scrolling news ticker going all the time in my taskbar and would occasionally glance at it. If something caught my eye and I felt like taking a break, I would read it. The appeal of it was that I didn't have to do anything special to fetch news headlines of interest to me. They came to me. I didn't have to switch to a different virtual desktop to see an RSS feed widget like I have (and got rid of) in KDE 4. I don't have to bump the edge of the screen to see my (utterly useless) Dashboard widgets in OS X. It was "just there". KNewsTicker doesn't seem to have survived the transition to KDE 4 and I haven't found anything so far that works like it that I could just park in my taskbar. This is yet another step back. You might think this is such a trivial thing that it's hardly worth quibbling over, and it might be for you, but like any user, I have my idiosyncrasies. This is, as I've discovered, a big deal for me. I feel disconnected from the world when I don't see those headlines scrolling by. It requires a rethink of my workflow to compensate for it and I don't have the time or the inclination to rethink this.
I've read many KDE 4 bashing articles and I hesitated at writing what might sound like another but I can't ignore the fact that KDE 4, as much as I really wanted to like it, offers no advantage to me whatsoever over KDE 3. In fact, it's a regression. I'm sad to say that because I'm more than just a KDE fan. I've developed some PyQt and PyKDE applications in the past and appreciated the technical elegance of the KDE architecture. The KDE 4 team seems to have spent lots of time implementing things I don't care about, like fancy window effects, transparency, etc. It's "cool" to be able to rotate a widget on my desktop but of what practical use is it to me to be able to rotate, say, an RSS reader 45 degrees to the left?
Having said that, I'd rather switch than fight with KDE 4. I'm not sure what I'll switch to but I can't see living with KDE 4 in its present form for the long term. The KNewsTicker issue above was enough to keep me from trying alternative desktop managers before. Now that I don't have it anyway, I might give a few of them a whirl. With my desire to "work with my computer, not on my computer", OS X seems like an obvious option for me but I really hate the loss of productivity I would have to incur over the stupid Apple keyboard mappings. Windows 7 is a wild card, though the emphasis on pushing the "everything is glass now" eye candy doesn't inspire confidence. (Glass tends to be fragile, too.) I have had maybe 24 hours of hands-on time on Vista and hated it. I regularly use XP and it has all the elegance of a Lada but even if I wanted to use it full-time, which I don't, I'd be investing time in something that is essentially dead and that I moved away from in 2004. It's the same reason that going back to KDE 3 doesn't seem like a viable option, though it might be at for least a few years until some of these issues are addressed in KDE 4.