Advanced task killer is probably the best task killer out there. I have the Sprint Hero, in my opinion, one of the buggiest of the Android phones. Every time I turn on/restart my Hero my phone decides that I will most likely need to use google maps AND sprint navigation right away. It does not think I need to know this info and will continue to drain my battery while letting both apps run in the background. Since I got advanced task killer I can know immediately what unwanted apps are open and close them with one click. It is pretty smart about what it thinks I don't need open like I want to keep my settings and sometimes marketplace open but every time I play a game or use an app and I just go back to the home screen instead of hitting menu>quit it stays open in the background slowing down my phone and draining battery. I can just open advanced task killer every so often and make sure I don't have anything unnecessary going on. I have tried other task killers but most of them either just didn't work well on my phone or just shut down when I tried to open it. ATK worked the first time I tried it, and i have even scene it downloaded on the demo phones at Best Buy. Also, a bug with my hero is that the android messages app (if you use it for messages instead of another app) can sometimes keep the phone running even if I put the screen to sleep resulting in a really hot phone and no battery life after just an hour. ATK got rid of that issue for me.