Eclipse has its strong points, but some people (like me) just don't like it. I can't really say why i don't like it, i guess it just doesn't feel right to me. I do like NetBeans a lot though. NetBeans looks and behaves more like a real OS X application than Eclipse IMO.

And if you're new to Swing development, Matisse (the GUI designer in NetBeans) really helps a lot... it makes it easy to develop java GUI's in the same way that Visual Studio makes it easy to develop winforms GUI's.

If you're a java developer (or are interested in getting started with Java) on OS X, i highly recommend giving NetBeans a shot. It's free, open source, easy to use and powerful.

note: i have nothing to do with the NetBeans project, i just think it's a great free IDE that deserves as much attention as Eclipse.