I was puzzling over this because he says there is no way to task switch from the keyboard and yet:
http://www.androidpolice.com/2011/08/12/tip-want-the-app-swi...
From what I understand, Alt-Tab task switching was delivered in the 3.2 update - can you clarify whether that's true or not?
Fwiw, I strongly suspect that the task-switching experience varies enormously depending on what you switch between. Firefox is probably a worst-possible-case because it'll use loads of memory and force Android to kill all other apps.