My battery became horrible recently on 2.2, and I have no idea why. When I bump charge it's fine, but other than that after I leave it on for a day or two (and charge it overnight) it dies very quickly. I use SystemPanel to monitor app activity and it doesn't look like anything's going out of whack app-wise.
I don't think an ATK is needed with 2.2.
However, there are times where I sure would like to kill a task...like the good old BB days.
For example... if I open music player.... often I can't get it to turn off... it will start itself at random times unless I shut the phone down. There is no way to "exit' the application.