Running KDE 4.3.1 on a PCL install. Works great!
It was just released yesterday and already Texstar and crew have it in both the "pass" and "public" repos. Not sure how it would work on Granular since I accidentally trashed my install some time back. But, if you're already running 4.2.x or 4.3.0 on your Granular install, this new release would be a must have.
For those who don't know, you need to change the "kde" on your PCLinuxOS repository line to "kde4." The easiest way to do this is from Synaptic > Settings > Repositories. Click on your PCL line and then edit the Section(s) line which is down below the main window.
Make sure your distro is completely up to date before switching to KDE 4. In fact, I'd try it on a separate install (another hard drive or another partition) so as not to gamble with screwing up your perfectly okay Granular install.
And whatever you do, don't do what I did. I used Parted Magic to wipe out my Granular install because I forgot what hard drive it was on. Just color me stupid.