I think a distinction needs to be made between some of these apps that we seem to be grouping together.
Some apps (atk, I believe) monitor device and system usage and automatically kill processes. I can see why this would be a problem if not properly set up. It needs to be monitoring all the time, and as standard, will kill apps arbitrarily.
Other apps (taskiller) are just a quick press of an icon to kill processes/apps when you feel it's needed. You can set it up to ignore certain things if you wish, but again, you need to set it up properly.
Lets just make sure we're all talking about the same thing here - and that we want the same results from it.
If I've had a heavy days usage, and then I try to play android golf (for example) it *sometimes* stutters and the sound stammers a bit. I come out of it, hit the taskiller icon and all is well again. I use it when I need to, and it's just one click. I have it set up to ignore twidroid, sense and a few other things I want left alone.
HTC One X
Nokia Lumia 800