Motorola Droid X
Dumped my task killer but...
Unless you see something in your notification bar (icon, gps pinging, etc) then the application is NOT consuming CPU cycles (not taking energy)
Instead it is in a "save state" in the ram consuming basically no power. If your phone needs more ram for something, it will kill it automatically and safely.
Android does not need any task manager, and it hasn't since 2.0 (and barely needed it before). If you have a rogue app that is draining battery when you back out of it, then uninstall the app and tell the dev to fix it.
And ATK doesn't work with froyo anyway, so you're good there.
ATK and programs like it show all applications currently in your memory, not just apps that are actually using your battery.
That is why they keep popping up.
How android works is that as SOON as you put an application in the background it pauses the app (unless you are listening to music/using gps something like that) and puts it in a save state in your RAM. This is what shows up in ATK.
They consume ram so when you go back to them, it's as if you never left. This is intentional. If your music player is still showing up in ATK 20 minutes after you paused it, it's because you've done nothing on your phone that requires that RAM to run, so the device was holding it there for you.
The other...
(continues)