I have just pulled my 20D out from a camera bag that was stored away in a corner and blown the dust off just to see if it is still working. This camera has hardly been touched in four years but much to my surprise both batteries are still holding a full charge. The body seems to be perfect. Obviously it's not a substitute for a 1Ds with high quality work but a few test shots quickly reminded me how much fun the 20D is.
Ditto - except my newer camera is a 5dII
I needed a second body to hang around my neck to save swapping lenses at a recent music festival.
It got heavy usage during the weekend and both batteries were as good as I remember them ever having been.
The handling is similar enough to the 5DII that with wildly different lenses strapped on the front it was easy to ignore the weight and multiplication factor differences between the 20D and the 5DII.
I never found myself in a 'If only ...' or a 'How do I ...' moment.
One of my spare 8Gb cards holds a stupidly huge number of 20D images.
Looking full-frame on my 1900x1200 monitor I was unable to tell which body had been used without checking.
The 20D was always able to make good use of top quality glass - and still is...
Mind you - I always put the 20D away before I needed to up the ISO....
And I think I may need reading glasses in a few years to cope with the tiny menu text .....
But the 20D is still a surprisingly good camera.