Now, the latest devel KDE is very very well. You can try KDE 4.2 beta 2 from a repo in this page. You can wait also to January 13th to the RC release or to January 27th for the final one.
From the KDE 4.2 beta 2 announcement page
Since the first beta, which was released less than 4 weeks ago, 1665 new bugs have been opened, and 2243 bugs have been closed. Since the release of KDE 4.1.0, more than ten thousand bugs were closed, showing a massive focus on stability in the upcoming KDE 4.2.0 which will be released in January 2009, 6 months after KDE 4.1. KDE 4.2.0 will be followed up by a series of monthly service updates and followed up by KDE 4.3.0 in summer 2009.