what ive noticed through my experience with 2.2 vs. 2.1 roms, froyo manages these apps in the background a lot better than 2.1 does. i used advanced task killer religiously while on 2.1, but noticed that when i switched over to froyo it ran just as smooth, if not more smooth than before. so now i just dont even bother with ATK, and let froyo/autokiller do their thing. im also noticing, even in the absence of ATK, i am getting much better battery life with 2.2 than i did with 2.1.
just my two cents.
EDIT: should have said i was on kaosfroyo. dont have experience on others.