I am doing fine on 2.2, I would check your programs and see what is eating your battery up. Chances are it is an app that is not 2.2 supported.
Check your battery usage and see if your phone is actually going into standby.
Also I could have sworn people have gone over this time and again, but Android does not and should not use a task killer, this is not Windows Mobile. Memory is handled very different.
In fact here is a great article on it:
http://geekfor.me/faq/you-shouldnt-b...-with-android/