My 1DXII has been very good so far at avoiding dust. Mind you, most of the time I use it for wildlife photography and I'm shooting with a wide open aperture, which makes all but the worst dust spots unnoticeable. I agree with Neuro's protocol for cleaning, in the exact order that he lists. The sensor stamps work very well, but I'd try all the other methods first.
Jonathan Huyer
www.huyerperspectives.com