I have been a Nikon user since 1974. Dyed in the wool. I have about 13 Nikon lenses. After I saw what the 5D MkII could do with a 20 dollar adapter to put my Nikkor glass on this full frame sensor, it was a complete no brainer especially at $2.5K. Moreover, the video capabilities of the 5D are unmatched. Just stunning filmic results. Consider this, shot on the 5D by a friend of mine:
http://www.vimeo.com/10570139