I just ran across a new Swing L&F called Nimbus that has renewed my interest in Swing. Its the first L&F that looks as good as OSX and Vista and it is entirely vector based. This is important because the resolution indepence means it looks good on the new high definition screens.
Additionally, all the painting is done with Painter delegates which are easily reused on custom components. This has always been a pain point for swing. Its hard to get custom components to blend with a particular L&F.
A screenshot to wet your appetite: