Battery drainage solution, I think
So, I have had a serious battery drainage problem, like most of hd2 users with wp7.
My battery usualy run max. 24h!
Now my phone run 2-3 days without charging.
I have just turned off connection with xbox live
So, go to the settings -> applications -> games, and turn off "Connect to Xbox Live"
I have 3G off
Data connection on (but mailbox, shares, weather ect. is updated manualy)
I hope this will help you...