Me and my gf both have a Sensation now(i upgraded from HTC Desire, and she a HTC Legend), we are both pleased with the battery on the phones, she uses stock Sense, and i use LauncherPro, though we did learn something from our older phones, the thing that drains battery extremely much is all the notification emails Facebook automatically send(gmail push), these are almost turned off to 100%, next thing is to turn off all syncronisation in the phone you don't use, ex. i use Launcherpro therefore i don't need the phone to update Sense's own weather, and so on.
We both normally charge the phone every night, but i guess my phone would last almost 2 days on days i don't use it that much.
I must say i am extremely satisfied with my phone, the thing that i dislike the most is the camera, or to say it in a different way, if i didn't know the SG2 had a slightly better camera i may have been more satisfied
