Seeing that I apparently hit a nerve for some people with my last post, here is the next thing that really annoys me every day in KDE4.
Those ugly passive pop-ups that appear on the display near the area where you have configured the "system tray" to be on the panels. From the beginning they were an example of uglyness. After quite some time they at least stopped to be drawn one over the other, so they are no longer totally unusable, but they still are not pretty.
One example: most of them are too small, so that the text they should show me gets cut off and I have to guess what the system wants to tell me.
As much as I detest GNOME, their unobtrusive notifications in the lower right corner are much more stylish and less disturbing than the KDE4 ones.
And it is not QT's fault: a proprietary application like skype, using QT, can do it in almost the same way as GNOME, so it is definitely possible.