Canon has a superior focusing system and a better price point. Even the best trained eye can not tell you the difference between high end Canon and the same quality of Nikon glass from a print.
The Nikon camera frames are built more rugged but the Canon is built very well and I am not about to start droping cameras now.
Take a look at the major sporting events and you will see more Canon products than Nikon. There's a reason for that.
The 20D kicks ass.
