I'm on Buzz, and you can find my profile here. That doesn't help you much if you haven't got a Google account, but if you have, you can use Buzz as a kind of Twitter replacement with slightly more features. The downside is that Buzz isn't great on privacy, and unless you find a bunch of hidden settings other people might be able to see who you are exchanging e-mails with. Not a secret in my case, but I do understand how that annoys some people.
For me Buzz is mainly one more amusing step of Google on the way towards becoming the next "evil empire" in the public opinion, like Microsoft. Besides privacy concerns other people are complaining how Google uses "bundling" with GMail to promote Buzz, an unfair competitive practice against Twitter. Now where did I hear that one before?