I have grown up with Nikon and have gone through several models starting from F801s all the way to a D3. I am a Canon user now, since earlier this year and I am getting used to its quirks and the somewhat less optimum operation of the bodies. My decision had nothing to do with the bodies (which are great from both manufacturers) but simply with the selection of modern prime lenses. Historically, Nikon has focused (in the top level segment) on large, heavy and expensive pro zoom lenses which produce great image quality but are ... large, heavy and expensive. The prime lenses have been waiting too long for an update (ultrasonic focusing, image stabilization) and have mostly been old designs. While Nikon have been working to fill this gap, I could not resist the lure of the relatively affordable, compact and light weight Canon "L" primes that produce fantastic quality images, not least because of their fast USM focusing, especially in the telephoto range (the 200 2.8 L lens, the 400 5.6 L lens, but also the 35 1.4 L and the fantastic new macro 100 2.8 IS II). Having gone through a lot of thinking and pixel peeping, I finally realized that I don't care so much about which make currently has the higher megapixel count or the somewhat better high ISO performance - yes these are considerations but in the end the light comes through the lens and that's what makes the picture. In this sense, I would say Canon is still ahead. (NB: I am very happy with the AF system on the 1D Mark IV).