Unity != Mandatory
With regard to GNU/Linux desktop environments, I used to be a big fan of KDE running on SuSE and/or PCLinuxOS until the KDE (SC) 4.x series came out, then briefly switched to Xubuntu and XFCE 4.x, then finally settled on Linux Mint under GNOME 2.2x/2.30.
The reasons? Well, there are a bunch, actually, but they can (mostly) be summed-up like this:
-- -- 1. KDE (SC) 4.x uses more resources compared to KDE 3.5 (the last major revision in the KDE 3.x series). KWin seems to be top-heavy, especially when compared to Compiz/Compiz-Fusion.
-- -- 2. KDE (SC) 4.x visual elements do not appear (to me) to be as polished and elegant as those that are provided with KDE 3.x, GNOME 2.2x/2.30, or XFCE 4.x; they have too much of a "cartoonish" feeling to them. The K Menu is visually jarring, and often doesn't seem to blend-in well with certain themes. I'm also not a fan of having to use a desktop gadget ("Plasmoid") in order to display the contents of the Desktop (or any other) folder.
-- -- 3. XFCE 4.x, while having the advantage of being both lightweight/fast and providing built-in Compositing, had the disadvantage of not having a central user preferences store and configuration dispatch system like GNOME has with GConf (although this is changing with the development of Xfconf, and may make XFCE worth another look in the future).
-- -- 4. XFCE 4.x had some pretty serious memory leak/stack smashing bugs a while back that rendered the environment almost unusable if you left the system logged-in constantly; after about 36 hours of continuous operation (whether or not a screen-saver was active), and with no apps open (other than panels/applets), XFCE would end up eating all available RAM and start forcing the system to swap heavily (this was on a system with an Intel Q6600 and 2GiB of memory).
So, given my experiences with both KDE and XFCE, I was left with either GNOME or LXDE. After playing around with a few GNOME- and LXDE-based distros, I decided to go with Linux Mint, and haven't looked back. The advantage of sticking with Linux Mint is that Clement LeFebvre has decided that the "traditional" desktop doesn't need fixing, and that they will forego both Unity **and** GNOME Shell. In Clement's words, they are looking at building a Linux Mint that uses the GNOME 3.x back-end framework and libraries, but not GNOME Shell:
-- -- Linux Mint Not To [sic] Switch To Unity
-- -- http://www.muktware.com/n/09/2010/440
So don't worry, I'm sure there will continue to be at least one distro going forward that lets us "traditionalists" both have our cake and eat it...