I'm an ex-2G owner and I just got a 3GS. I have been using it for ~12 hours after charging it full, and have noticed that the battery life is pretty terrible. I turned off 3G as well as push/fetch, made one 6min call, did not use data, and just played around with a few apps sporadically. The battery life went quickly down to 2% after less than 2.5 hours of light use w/ about 10 hours of standby time in airplane mode. Specifically, location services seems to have the biggest effect on it. It makes sense when you're in an app that actually uses GPS/Cell to get your position, but why would it eat battery when I'm not using any "location features"? And to be able to use compass/gps you have to go back into settings to turn it on again, very annoying. I'm impressed with its speed, but the battery life is apparently worse than the 2G iPhone, which was already horrible. Edit: Some people suggested that there may be a "break-in" period for the battery, so perhaps (hopefully) the battery life will increase significantly in the next few days.