[lmm]

Personal experience only:

KDE - mostly fine, I use it, but it still won't let me set a default transparency the way I could in v3.5. If I could find a supported way to run 3.5 I would.

Gnome/xfce - gtk-based so backwards button order, requires magic typing to let you enter a file path in an open dialog, probably other things that would annoy me if I put up with those any longer. Gnome also has registry-based configuration, and neither has a decent well-integrated browser or email client; firefox/thunderbird/evolution work as standalone apps but e.g. drag-and-drop doesn't work as reliably as on KDE (or didn't when last I tried), proxy settings have to be configured individually, etc.

xmonad - urgh. Underdocumented if you don't want to learn haskell, and doesn't even have a browser etc. last I looked.

There's not a whole lot wrong with KDE, but for my use cases it's still worse than it was on version 3.5 (the aforementioned transparency problem, and the lack of a music player with the features of amarok 1.4 are my main issues). That's the most irritating part.