KDE has anounced the availability of KDE 4.0 RC1 – get it while it’s hot!
Alternately, you can grab the Debian KDE4 Live CD which should be updated shortly with the latest release.
Caution: As with any beta software, things can go wrong. I’m doing something that shouldn’t be done by mere mortals, all for the sake of experimentation. And for posterity, I did screw this up once. But I was able to recover from text mode console and resume. I’ve ommited those steps. 🙂