doesn't a beta SP or even a leaked Beta completely defeat the purpose of an SP? I mean, the SP add some features, but also fixes bugs that were not addressed in the original due to lack of time and experience. Now you go ahead and install something that isn't fully tested yet either. Also not sure how it will play with any other Windows 7 updates and SP.
Unless one has problems with Windows 7 that need immediately resolved by the SP, I don't get it. i used the RC1 because it was so much better than Vista, so it is not like I mind trying out new things.