I’ve emerged my copy of KDE 4.2 last saturday and I’ve been using it since then at work as well as at home. Apart from the occational crashes (it’s a .0 release after all) it’s running really smooth. It’s way better than 4.1.x which I was running for the last year on my notebook at work.
What I’m mostly missing are configurable items. Like remembering last used directories and disabling the generation of thumbnail-files directly into the root of your home directory.
But these things are easily fixed (and give me an excuse too look into the KDE sources a little bit closer).
And the one thing I really like is the new KDevelop with DUChain. It’s really cool to have your meta-template programs evaluated directly in your IDE. It still lacks support for documentation and gdb but these things seem to be coming along in the next two or three weeks (from what I’ve read on the kdevelop-development mailinglist).