I switched to using Subversion a few months ago and I love it. So much so that I regret not having made the move sooner. Prior to Subversion I was a CVS user. Regrettably, I still am in many ways. SourceForge does not provide Subversion services as an alternative to CVS. I maintain one project on SourceForge. I'm discovering that I like Subversion enough that I'd consider switching for it. My understanding is that java.net also is a "CVS House" for the moment.

It looks like it might take another year or two before Subversion availability for open source projects becomes mainstream.