Well, yeah. Android moves things out of memory when there is memory pressure. You have to wait while this happens, and most currently-existing Android devices are massively underpowered. When you use a task killer, you are spending the time when you press the "kill" button, instead of at some other random time.
Android users that use task killers are like Windows users that disable their pagefiles.
Bottom line is that it works. The theory behind how it should work may be nice and dandy, but the reality is that it doesn't work as advertised. Whether it's because I haven't waited enough (why would I need to wait in the first place?) or whatever other reason, the unit slows down over time quite a bit and killing processes brings it back to life.
The fact that current devices are underpowered has nothing to do with the issue. N1 works just fine after a reboot but slowly degrades in performance. If it was "massively underpowered" if would not have worked properly in the first place.
I also don't understand why there is no easy way to disable some applications from auto-starting. For example I've never used the MP3 Store application, but it always starts up. There are a number of similar apps that do this and to my knowledge there's no way to prevent this from happening.
The N1 is not one of the underpowered phones; the Dream and Magic are. The fact that you need to kill "processes" (which is not what the task killer does, btw) means that there is a bug in some app you use regularly; narrow it down and fix it, and your phone will be fine.
Android users that use task killers are like Windows users that disable their pagefiles.