The deal is simple:
1. Murder certain things and your phone becomes unstable.
2. Task killers all by their lonesome often cause instabilities - depends on make, model and then you, the user.
Android wants to kill tasks when it finally decides they're just not needed.
Some tasks are not well-behaved - so you might want to nudge them over the edge to annihilation.
If anything, I've found that Advanced Task Cleaner Pro (not to be confused with the ATK killer) does not cause instabilities on my Evo.
As for why not everything showing up in the Android running services list - that list is trying to save you from yourself trying to kill too much of the wrong things.
Some apps are simply written and installed in such a way as to not show up in that list.
Use Automatic Task Cleaner Pro as your last resort to managing your phone.
So - what is it you're trying to accomplish - really?
