I love these threads about multi-tasking.

"REAL" multi-tasking isn't about having a half-dozen applications on screen at once and having the ability to switch from one to the other.
"REAL" multi-tasking is about having a half-dozen applications on screen all doing something simultaneously, just like I used to do on my Commodore Amiga 19 years ago.
I'd have Imagine or Lightwave rendering a scene of objects, Vista Pro rendering the landscape that they are going to sit on, both churning away in the background while I'm working in Personal Paint on the textures that are going to be mapped to the objects.
That's 3 graphically intensive programs all "working" together and nothing sitting idle in the background.

Here's a good way to test muti-tasking on the N900:
Start Bounce Evolution and let the intro animation kick in, then hit Ctrl+Backspace. Now start a video in KMPlayer, enable fullscreen and hit Ctrl+Backspace again and see what happens.