For those who have decided they'll only ever own zoom lenses, I'd highly recommend this lens. It will provide an inexpensive education in photography that you couldn't enjoy with a zoom. How can that be? First, this prime introduces the concept of zooming by moving the feet. For me at least this physical element forced me to think more carefully about composition that ever before... and this I'm sure you'll agree cannot be a bad thing! Second, the large aperture (show me your f/1.8 zoom) introduces *thin* depth of fleid challenges and that great subjective blur known as bokeh... Adjust your camera to Av (aperture priority) f1.8 or full manual and enjoy the challenge of photographing with *thin* depth of field. ("Go for the eyes Boo, go for the eyes!") You'll get to see great bokeh as well! Third, and for me at least, finally, this lens allows for nice low-light/indoor portrait photography. The f/1.8 aperture together with the 20D's quality high-iso values is an amazing combo... you hardly need flash, and if you do use it you'll get a picture that looks all the world like it was taken in pleasant sunlight. For this last reason this lens moves past raw education and must claim keeper status with even the most die-hard zoom-only fans (I was one of those too once!). Get it, enjoy it, and keep snapping away!! Oh by the way, if you're even 1/2 interested in macro, you should know that the 50mm f/1.8 has reasonable (but not 1:1) magnification too.
For those who are more than a little interested in primes... I'm guessing you've enjoyed one or other of the Canon 50mm range already.
To sum: a great inexpensive photography lesson and useful low-light portrait lens. I listened to the reviews and have NOT been disappointed! You'd be mad not to!