Honestly, I haven't really hit any KDE bugs in a -very- long time, but then again I mainly use it on my laptop for actual developer workloads. KDE 4.10 is a pretty nice release with decent features. BTW, did someone really claim that Unity, Canonical's bastardized buggy hack on Gnome was really a contender to either KDE or Gnome by itself?
My school has KDE 4.3 installed (rhel6), and it is a terrible experience compared to 4.9 on my laptop/desktop. Many of the features that I miss are things that were added in 4.8 and 4.9, such as improvements in Kate, Dolphin, and Kwin, as well as greater stability and flexability in Plasma. (the alt+f2 launcher has gotten loads better, not sure when the changes happened, but it wasn't improved until at least 4.5)
Jesus, never tough there where so many KDe haters.
I love it, kill me if you want...