When on my first trip with Thunderbolt. Despite the fact that inside of hotels/casinos in Las Vegas I got almost no 4G service, and sometimes not even 3G the battery did pretty damn well. I think I got 24+ hours on a single charge two days in a row with moderate use. I've even turned the brightness up from 0% to around 7%. In bright sunshine I'll go as far as 25%. It's a relief to finally be able to do that. I also found a great brightness widget that allows for instant changing to any %.
Glad to be back in Phoenix though, where I get 4G almost everywhere.