Originally Posted by quantum-x

Two caveats - the fact it isn't USMII focus - which means it's slow and noisy - neither a good factor for a lens, esp a modelling lens.

I looked at this when I was in japan, and went for the 50.
On the 20D, the 50 will be an 80mm lens, so you have a perfect portrait lens right there.

For wider scenes, you need and EF-S lens that can do wide angle - perhaps the one Woj suggested, or even the 11-24 [from memory]

Honestly, if you've got the 20D and you're not buying Canon lenses, and Non 'L' series lenses, you're putting bad glass on your camera. Simple as that.