Foreword - I’m writing this review about MY experience of the 20D. If you want technical reviews, go search google...
I’ve always wanted my camera to do what I wanted... I always found that digital point-and-shoots restricted me in aperture, shutter speed, flash sync, etc settings.
When the 20D became available and AFFORDABLE, I went ahead and bought it. It is just like a professional SLR. Only difference is - it has a few features lesser than a professional SLR. And the biggest difference - it’s a APC sized sensor. Which means the sensor is not equal to a 35mm film SLR. So the maximum print from the 35mm film will be 1.6 times bigger than the 20D.
Question is - does that make a difference to you. Unless you print a 18x20 prints every day and you have gorgeous models visiting you :-) , The 20D is sufficient for the amateur and hobbyist. For pros, this is still good enough to be your second camera.
If you still want a full-frame i.e. 35mm film equivalent camera, then Canon just released the 5D. it has almost all the features of a pro-SLR camera. AND it is in the $3000 range. The 20D will hit you at $1100 to $1400 range.
Photos come out much better. I’m learning new techniques every day of taking better pictures. One thing you have to remember, don’t pick this camera only for wedding and occasion photos. The 20D carries so much potential that you will look forward to going out on weekends just to experiment with this camera.