KDE is GREAT, if: you like tweaking and customizing things. The out-of-the-box KDE is lacking. It's like it wants to be a mix between GNOME's opinionated setup while giving you a lot of flexibility. This means, at least for me, KDE needs a lot of stuff "undone" to get it back to a usable point.
If you hate tweaking, and want something akin to the Win2k UI feel, XFCE will get you there effectively out of the box.
Personally, I'm still using Unity 7 on X11, but as that DE's project is now seemingly dead again, I keep looking for a replacement. This one also looks pretty interesting!
I would really like to find something that handles fractional scaling as efficiently as Unity/Compiz. That, the dash, and (I'm ashamed to admit) wobbly windows are what keep me using it.