I was a Canon shooter for many years, and following a burglary, and having AF problems with a couple 1D Mark III's I switched. I was replacing everything, so I had a clean slate. The switch is discussed often, but I haven't heard anyone mention the transition being a bit painful. Consider the the lens mount. Canon mounts with a right hand turn, Nikon - Left. Zoom in/out - Opposite rotation of the lens barrel. Manual focus, opposite. Exposure compensation dials, yep, opposite rotation of the dial. The flash card even mounts in the camera opposite than what you used to. It's taken me several months to mount a nikon lens without having to look and think!
Image quality - I can't appreciate any real world differences.
A number of Nikon lenses are quite old. My 85 f/1.4 and 50 f/1.4(just updated) are screw drive AF. Not bad, but not as fast as Canon (subjective). The 85 is something special though. Makes for stunning portraits.
Tele: The current 70-200 VR seems comparable to the Canon 70-200 f/2.8 (also rumored to be updated soon). Although it does suffer from some considerable vignetting. The 600 f/4 VR has been on order since Feb 2008 - purchased a used 600 AFS in the mean time (ever seen a Canon lens on backorder?). The 600 AFS non VR focuses and handles just as well as the Canon. The new 600 VR is around $2000 more than the Canon version. I'm sure its not $2000 better.
Autofocus: Comparable, and possibly better. You couldn't possibly be disappointed, but to say its better, possibly. I also shoot wildlife and have found the D3 wonderful for birds in flight.
All said and done, I love the Nikon and after a Nikon year, Canons now feel backwards. Would I make the switch again. No. The The daily handing/operation differences are many, the quality, performance differences are few.
The biggest problem with the switch, my shooting buddy uses a Canon. No more cheap backup in the form of sharing lenses and bodies on a trip.
Stick with the Canon. Who knows, you might come across a cheap, and hot, 1D Mark III, 600 f4 and a lot of other nice glass.