I’ve just taken up using Twitter. So far so good. Two points though, one of which isn’t the fault of Twitter but:
1. DowningStreet doesn’t bloody shut up!!
2. The site has complained about being snowed under 3 times so far. They could sort this easily by using Django instead of Rails. 
Other than that it seems alright. For Rubyists you may be interested in the Twitter Rubygem by John Nunemaker: Twitter.
gem install twitter
P.S. Green as in: new, rookie, etc
