I have 3g activated (though it uses wifi in the house)...and I get a full days' (read: about 24 hours) worth of battery life in moderate use with weather, news, and email apps going. The biggest change I made that seemed to have a dramatic impact on battery life was logging off of skype (and I never set up any other IM accounts). The constant traffic needed for the keepalives in IM protocols really sucks the juice.