I got fed up with the Vista-esque themes and changed back to the regular Kubuntu ones. I've also ditched the themes for Firefox and Thunderbird, but Firefox I've given the great KDEFF theme, which fits in well with KDE.
I've also given Tasty Menu another try. The Kubuntu version seems to have improved a lot since I last used it - it behaves like a menu now, and you don't have to close it down yourself anymore. Here's what it looks like:
Now, Tasty Menu is a lot tastier than it was!