You'd be much better off using battery graph as it shows CPU usage and wifi/gsm connections.

Autodisconnect is in extra's at the moment and defo helps with saving battery life. It's a shame that a higher capacity battery wasn't used but if one uses Autodisconnect then less time is spent using the 3g connection as this drains battery like a pig! I sometimes have facebook,msn and skype turned on and this can rape the battery a tad but sticking the phone on 2g all day one could easily get 24 hours, internet would be slow but for email, calls it's perfik!