I charged my battery full overnight got up this morning at 9am, browsed the internet, used usa today app for about 20 minutes, then went to the mall, while the wife looked around I was running speed tests, and browsing facebook and the internet, did a couple of sms' and a couple phone calls...now all in a 4G area battery at almost 3pm = 81%...I would call what I did moderate use, no GPS, no Pandora, the extended battery seems to be holding its own
That's why apps should help considerably, where something like Locale or Tasker will only enable LTE when you are in an area with a good LTE signal. In other words, define a radius and if you get outside of that radius the LTE radio gets shut off.
I played with the demo Thunderbolt at Best Buy. I had to cut it short after a few minutes as the battery died. The sales person said the battery does not last well. They charge it all night and between customers, but it will not make it through the day.
My battery life is not great, but it will last with moderate useage from about 9 - 5 before it goes into the orange bar. Last night I sat and listened to music on the phone for about 45 minutes and was very surprised the battery didn't drain as much as I expected about 25%. I do live in a 3G area and am usually in "plug" distance but am considering the second batter as a backup.