Hi. I have been monitoring phoronix for the past 5 months and this is my first comment. I have already downloaded and tried the 4th release of KDE.
So far I have not been pleased with this release.
Hopefully this is because I have installed KDE4 onto a mythbuntu system that had gnome preinstalled (essentially a dirty system - which was not configured to be used with KDE4). I will try installing it onto a clean system and retesting this. If any of my issues remain after the retest, I will be sure to post some bug reports.
The main issues I had were that the desktop icons became widgets and as a result they are buggy. (When I mouse over all of the icons a bunch of them highlight and don't unhighlight - until I go over each one slowly). Also the desktop was extremely slow. The Desktop effects (like rotations and movements) were slow and choppy. (like the CPU was 200% in use. (Yes that is 200%). I had the entire system freeze twice. No buttons would work (ctrl+alt+f1 or ctrl+alt+backspace) - I had to wait 5 minutes an 25 seconds before the system unfroze.
Other than that the issues I experienced and the fact that the icons have now become widgets the desktop looked great, the wall papers were very nice and juicy too.