I have the phone for 4 months now and this is my point on the battery. First off pre amber-time, usually it would last the whole day from 7am till midnight with medium use including 20 minutes skype with the webcam, about 10 - 30 min talking on the phone and typing messages from the time to time, well you can count 1 hour of facebook beta app and some podcast streaming too. The setup was simple, everything is off except wifi and 2 background services (battery pro, accuweather). I was pretty fine with it, the battery almost never was below 20% before i plugged it into the charger.
After the Amber update (i flashed it) few things changed, battery pro was giving me alarms (set to 20% discharge rate) all the time, Facebook Beta App only would discharge the phone at 28 - 32% which was never the case before, i got used to active Skype being a drainer when used to video chat, but now it was huge. After i finished skyping the battery app shows almost 40%. The fact that i want to go out and my phone is almost killed got me thinking. Hard reset was no option, even tho i wanted to change some other things regarding my account. Then i got the terrible idea MS might be a resource killer, so i uninstalled all the apps i never touched like 50 of them and left only the ones i do actually use (apps now 2.7 GB). I logged out of the Facebook Beta app and started using the mobile site, same with youtube and similiar stuff. And wonder it helped, the situation is now like before and even a bit better since i m using skype for a quick session when i go to bed. And i use facebook mobile more cause it uses less battery (around 15%). I also turned the youtube and weather background services off, i dont really need them at standby. I dont need to note that i dont use MS stupid intergrated chat service, first off i recive SMS a lot and 2nd its pretty ****e. Now will wait for the GDR3 update and hope the good comments on here will be proven on m device too.