It's been about a week since we announced Subversion availability on RubyForge - and a clear pattern has developed. Out of the fifteen projects that have been submitted since then, twelve of them have chosen Subversion over CVS!
Overall, only about 5% of the RubyForge projects are using Subversion - 61 out of 1112. That number is skewed by dead projects, of course, and folks are continuing to convert over, but anyhow, it'll be interesting to see where that percentage is six months from now.
For the record:
Not many folks using the Wiki capabilities either - mostly due to the cursed Wiki spammers, I daresay.