After using KDE4.1 for some days I’m quite satisfied. Most of the applications perform very good and are stable. However, there are still several annoying bugs I have to deal with. They prevent me from recommending KDE 4.1 unrestrained to others.
The first bug when I login is that KWin crashes instantly. Sometimes it takes the whole X Server down but most times it just notifies me that it has crashed and is restarted. Then I can continue working. I did try to make a proper bug report, but as soon as I install the debug symbols KDE becomes unuseable at all. I’ll have to investigate this further as I have much interest in getting this bug fixed.
The second most annoying bug regards Dolphin and Konqueror or, the be precise, the metainformation framework (nepomuk or strigi, I’m not sure). As long as the “information” sidebar is enable Dolphin crashes instantly when I move the mouse over some file (not directory) and the backend tries to load the related information. This is super annoying but fortunately there is a simple workaround: just disable the information sidebar :)
But apart from this bugs I have to say: KDE4.1 rocks!
I especially like the new user interface, KWins compositing features, Dolphin (as long as it doesn’t crash) and Kopetes OTR plugin.
There are also some slight difficulties regarding KMail, but I hope these will be adressed until KDE4.2 when KMail is supposed to be based on Akonadi.