IDEA 5.1 has been released to much rejoicing. Well, I rejoiced at least. I've seen some occasional instabilities with 5.0.2 but I think I've traced it to cache corruption/staleness. IDEA would suddenly fail to parse my code and I'd get stack traces involving the PSI code in the error tracker. The workaround is to shutdown, delete the cache from disk, and restart. I don't think this is fixed in 5.1 as I just looked at the bug(s) entered against it but hopefully at least the Jetbrains guys are aware of it now. 5.1 is a bit snappier with some nice new features. You should definitely check it out.