I use
IDEA at work (Windows XP Professional), and I ran it at home once just to try it on OS X; once I had it running, it worked as well as it does at work. For any assistance you might need to run it under OS X, check the newsgroups at news.intellij.net via your favorite newsreader. I'll summarize IDEA by saying that it is very powerful and feature-rich without getting in the way at all! Finally, the price, $400 when not on sale, is virtually impossible to beat!
Craig