I've never made a secret of the fact that I'm not particularly enamoured with what KDE4 has brought me so far. I want to use it, but it never lets me. The biggest issues are performance and stability. Stability because crashes are frequent - when I tried the latest version a few weeks ago, even the crash reporter managed to crash several times. It's like crashception. Usually though, the crashes often seem to be subsystems that don't do anything important, so you can generally just go about your way - just don't use KDE4 for anything serious.
The performance issues are of far greater concern. They seem to focus pretty much exclusively on Kwin, and have been a staple of KDE4 on my machines since the very first few releases. I've run KDE4 on several different computers with different graphics cards by different brands, using both open and closed source drivers and different distributions, but the one constant is abysmal Kwin performance.
Some people have suggested I turn off most of the effects, but you know what? I currently have a quad-core Phenom X4 2.2Ghz computer with 8GB of RAM and an onboard ATI Radon HD3200 video card - I'm not going to run a Windows XP-like tearing graphics experience with such powerful hardware! Sure, the video card is anything but exotic, but heck, Windows 7 and GNOME/Compiz offer zero performance issues, even when playing 1080p video, so why should I excuse KDE4?
For those of you who are also experiencing performance issues like this, or those of you who simply don't like KDE4 for whatever reason (I actually do like KDE4), you may be relieved to hear that the power of open source has made it possible for the KDE 3.x branch to continue development in the form of the Trinity Desktop Environment, which has just pushed out its
first third release, version 3.5.13.
Other than new patches and fixes, the Trinity project also includes fixes, patches, and enhancements coming from several distributors such as OpenSUSE, Chakra, and Ubuntu. The changelog is pretty impressive, and the KDE4 compatibility is nice too; you can install Trinity alongside KDE4, and KDE4 applications will be recognised and run just fine inside Trinity.
Binary packages are available for Fedore, RedHat, Ubuntu, and Debian. Of course, you can always build it from source yourself.