Most reports I've seen say that SP2 hasn't affected anything. There are, of course, the programs Microsoft lists, but many have already been patched.
My suggestion... wait a couple of months before upgrading. It's an important upgrade, and shouldn't be ignored. The software problems come on the part the software companies themselves, not Microsoft. However, I'd wait for an SP2a or similar update. If you have a firewall and an antivirus program, you're already doing your part.
I have been using SP2 since Release Candidate 2 and have had absolutely no problems with it.
YMMV.