My Solution for battery problem after 2.2 automatic upgrade.
I take the suggestion to reset the handset to factory setting first. Then Start added different features every hour and check battery usage. finally, I notice as soon as I enable push on exchange, the battery will run down many times faster than before. And by connect wifi, I can monitor the data usage on my ddwrt. and found out automatic(push) use a lot of data. and that explains why the battery life runs down faster.
This also explains why someone's battery life didn't affected by the update, because they are not using exchange service. Please let us know if you have the battery problem (phone runs hot, battery run out in 4 hours even not in use), please let us know if you also use exchange for email with push.
Solution,
Suggest to change :
Email -> Menu -> Account Setting ->Email check frequency ->Every 10 minutes.
After change to this setting, my battery actrually runs longer compare with 2.1 firmware.
Hope it helps.
-Jet