When I installed 2.2, the settings for all sync's was changed to the most frequent sync frequency. I recommend that you do the following:
1. Check each application that has sync frequency and reset sync frequencies to what you need them to be;
2. Check the Sync frequencies in Settings and set as you need them
3. If you have the Facebook app, update to the latest version; if you do not really use the Facebook app, then remove it.
4. Set your task killer to not run all the time, only when you want it to run. I run my task killer "on demand' in order to "kill" a runaway app and the task killer.
These steps greatly increased my battery life under 2.2.
I did the manual update and it was running laggy and hot. Took off all the apps I'd accumulated but didn't use, trying to get main memory up to where that wasn't an issue - around 60-70MB. Then removed my task killer, Screebl and Lookout. Removed facebook. It seemed to be running pretty well then. Put Screebl and Lookout and Facebook back, but not the task killer. Froyo doing a pretty good job of managing memory itself, it seems.
Things are much better now. It did have the battery problem (wife's also) when we tried to do a big app download over 3G while traveling.
Since then, I've rooted, experimenting with SetCPU to OC it, and looking for a good replacement ROM, once I'm sure the OTA updates have concluded.
I experienced the exact same issue. Charging would take at least 8 hours, and the phone would be dead within 3 hours. I was running Advanced Task Killer, uninstalled it, and had the same issue. I had not ever started the FB App, but it was running, and I stopped that. I also tried reducing the Exchange sync frequency. Even still, you could practically watch the gauge go down, and the phone was incredibly hot. You could leave it dark for 60 minutes, come back, the phone would still be hot and you'd have lost at least 25% of the battery. It was so bad, it reminded me of my old HTC Titan running WM6. :P
After backing everything up (Astro File Manager is an easy way for that), I performed a hard reset and data wipe. I did have to re-activate the phone, but since then 2.2 has been running fine, and I am holding a charge as well as ever. Exchange is on push, ATK is still not installed, and everything seems OK. I'm going to slowly go back to playing around with my settings and see if I come across anything else that might have been causing the drain.
The build I am showing is: FRG01B
Hope this helps someone!
I received the 2.2 OTA and i am having the same problem, my battery drains so quickly, also my phone takes so long to respond sometimes, along with the fact it keeps opening up programs.
Anyone with Battery issues after 2.2 take a look at your processor activity. Is your phone warm or hot? Then its running all the time. Try system panel (lite). be you will find your processor pegged at 100% and running at 500+mhz. I did and a hard reset seemed to fix it.