Following on from the discussion earlier in the month about Windows XP Service Pack 2 changes, we've now posted the first Release Candidate on the web for download. The good news is that it's available to everyone, MSDN subscriber or not, so you've now got a couple of months to check your application for compatibility before it is finally released. Once again, I recommend taking a look at the "Book of SP2" for detailed discussion of the changes that might affect your application.
I've been running this release on my machine for about a fortnight, and can report that it's stable enough for use on a primary development workstation. Bear in mind that support is only available through newsgroups until the final release of the Service Pack ships.