I've seen a lot of posts from new users recently stating how these task killer apps are wonderful and improved their speed and battery life no end. I say, rubbish! Android/Linux doesn't work in the same way as windows and just because applications are still cached in memory it doesn't mean they are using up CPU cycles or battery life. Sure, I started out using a task killer app when I first got the phone too, but I haven't done for a long time now. I haven't noticed any decrease in performance or battery life since stopping using it. Try it yourself for a week or so.