Isn't that usage just an estimate though based upon a history of your usage? So by resetting the phone you are just resetting the stats counter possibly?
Partially true. It seems to estimate the remaining time based on an average of recent load/usage.
Regardless, in my case the battery life is staying put at it's new level. I started the 3rd day of use since my original post with the meter reading 1 day 7 hours remaining (where my previous best was 10 hours). So, today I unplugged from the charger at 8am, and used it fairly lightly (sent a few emails, twitter, fb, and google mail's all logged in, location on, wifi on, 3g on), and it's not 6pm (10hr later) and I'm shoing 76% battery remaining/21 hours remaining.
Happy!
I've only reinstalled a fraction of all the original crap I had on my phone, but still a few tasks that run in the background and update tiles/push, etc: Carbon (with full notifications activated), Facebook (same), and Wonder Reader (same).
Interestingly, yesterday I re-installed "Armed!"the only game that I really played, and instantly I saw my battery expectancy drop back into a terrible zone of approximately 10% per hour. Even with notifications off and the app not even running in the past hour something was still sucking life from the battery at about 3 times the regular rate. I uninstalled the game, and battery life is again normal. Smoking Gun perhaps? I suppose I would have to actually let the phone drain down once with the app installed and once without, to really know... but I need to use my phone and don't want to just use it for experiments.