Swing has limitations. Here's an article that I think summarizes the problems pretty well. Even with the new Synth look and feel, I don't think it stacks up compared to what's being done in Flash.
However, I like Java a lot better than Actionscript, so here's my attempt to remedy the situation: a new widget toolkit that uses as little of Swing and AWT as I can get away with, and as much of Java 2D as I can cram in.
The idea is not to try to replace Swing, but to create a new component set for a different kind of application--the kind that need to be developed fast, where presentation and adaptability are of paramount importance. Instead of exhaustive architectural openness, I've gone for the Kiss principle. I'm aiming for my component set to be easy to use, intuitive, infinitely re-skinnable, and ready for use in thin-client apps.
Click on the icon below to see a small demonstration of what I've got so far.
The only Swing components in use here are one JFrame and one JPanel.
You may notice: