Actually, I just got an extended battery for my Vibrant this week. I charged it up and put it in at 7AM yesterday. 25 hours later under moderate use (surfing the web, IM sessions, phone calls, checking weather, etc) I am at 49%. (a predicted) 48 hours with moderate use is ok with me.
The battery life in the iPhone4 is certainly better than the stock battery on Android phones, but being able to swap in a new a battery and boot in less than 30 seconds is an ok substitute (especially if you're on the move a lot and won't have access to chargers).
I love how Android users include standby time when talking "usage". I guess your phone cant seperate out standby and true usage?