D3x has amazing image quality, handled correctly (on a tripod, low ISO). I get 24x36 inch and larger prints of high detail landscape out of it all the time (and sell them in galleries) . The fact that a D3x gives its best image quality on a tripod (or handheld at a very high shutter speed) is not a flaw in the D3x - it is simply a reflection of the fact that that much resolution is going to show any tiny vibration. Canon's new pixel monster will be at least as bad in that regard. I find Nikon's interface and short lenses to be superior to Canon's (but wish Nikon had Canon's long glass), plus the D3x is a decent-sized step up in image quality (not just resolution, but phenomenal dynamic range) from anything Canon has right now. It'll be interesting to see what their new camera does - I've heard rumors of an oversize sensor on the new Canon (but the same rumors swirled about the D3x, and it came out with a conventional 24x36mm sensor). I wonder how radical the new Canon will be - the D3x is in fact a very conservative design apart from the sensor and AA filter (it's a D3 in every other way) - will Canon follow the same path, or will they release something that is unexpected in some way? Interestingly, both Nikon and Canon are on three year cycles with this type of camera, but close to 18 months apart, so they'll always be playing leapfrog (unless one releases something unexpected that the other has trouble catching)!
-Dan