Surprisingly enough, no one has flamed me yet for being disappointed with the quality of KDE 4.0. I must try harder. I used to be able to attract flames much more easily.
Well, I've had KDE 4.0 on my machine for a day or so now, and I'm getting used to it. I've switched to running AIGLX so that I can use KWin's OpenGL mode instead of the XRender mode, and it's a lot more stable, although I can't run Google Earth any more. With the OpenGL rendering, the desktop look great, and the beauty of the desktop alone is probably enough to stop me switching back to KDE 3.5 at the moment. A few times I have clicked on a window only to have it completely disappear without warning - not sure what that's about. There are a few niggling little bugs in the behaviour of a few things, but I'm sure they'll get sorted in a minor release before too long. (Such as icon widgets not working with a graphics tablet, not being able to hide the plasma blob, konqueror not loading images or styles, etc.)
I am inspired to try writing some plasma applets to do things properly. And when I say properly, I mean how I want them to work. I've had a look at some of the source for existing stuff, and it looks relatively easy, so instead of writing any more of this, I'm now going to go off and write some code. Perhaps. If I can stop gazing at the beautiful desktop.