I do most of my development on a Windows box (even though I dislike Windows and much prefer Ubuntu) so I've not noticed this problem before, but it seems that Java software that uses non-OpenGL graphics runs like a dog on versions >= 8.04 of Ubuntu.
One thing I like about Java is that it generally runs identically on most platforms, but sometimes something comes along which stops that "feature" dead in its tracks. The KeyPressed/KeyReleased bug was one of these, meaning I had to write special code get around it. If you don't test software on all the platforms, you won't know about these issues (as I am finding).
I've only got two Ubuntu boxes to test on, and one of these is a VM (which can add its own set of problems), so I'd be interested if anyone else experiences this. And I'd really like to hear from anyone who has a solution!