*Edited to add - for those comparing the 1DII to the D1x, come ON. The D1x is over 3 years old an the 1DII is one of Canon's freshest bodies. Not to mention as for speed comparisons, the D1x was never intended to be the speed camera, it was the studio camera. Let's compare to the latest Nikon, which is what I do.
I can't argue that Canon isn't in some ways better. BODIES isn't one of those ways (don't even get me STARTED on ergonomics, and the build quality of the 300D & 350D vs. the D70.....anyway I digress) Nikon is not big enough to keep up with the cost of the kind of R&D it takes to keep up in the digital age (notice how slow their development cycle is - what do you think would happen to Intel if they took that long to respond to AMD?). Which was a problem with their LBCAST sensor in the D2h, which, I'm sorry guys, we'll be honest, was not great. It did a lot of the things they said it would, but sacrificed noise performance and was not up to the standards of the wonderfu D1x as far as colors go.
However, that's now back to being irrelevant like it was with the D1 series. Nikon bought their sensor from Sony again for the D2x. And it ROCKS. So you can go back to worrying about who has the better bodies (Nikon) because both brands have good sensors again.
The small number of testimonials, reviews, and comparisons I've read so far, although in some cases not 100% scientific (which, sorry photography isn't scientific, MTF tests are the least useful lens tests for example), suggest that the D2x can stand toe-to-toe with the 1DsII and keep up and in a few cases squeak out a lead. Obviously the 16mp 1DsII produces slightly more detail than the 12.2mp D2x (4992 x 3328 pixels vs. 4288 x 2848 pixels, about 1.5"x1.5" difference in a 300 DPI print, already not worth $3000 more for the 1DsII in my opinion). However, looking at Bjorn's comparison, I agree with his conclusion that the D2x is a bit sharper. I suggest you read this review, it really makes you want a D2x, but he is EXTREMELY knowledgeable and is NOT shilling for Nikon.
www.naturfotograf.com
Now as for the 1DII. I won't try to convince you to get the D2H/D2Hs over the 1DII. The new sensor in the D2Hs is supposed to improve the color and white balance shortcomings of the D2H, but they said nothing about the noise, which lets face it was a problem with the original D2H. Plus, I'm sorry to all those "4mp is enough" people, but even if 4 is enough, 8 is better. That's like 1st grade math right there.
A quick note on specs.
1Ds II - 16mp @ 4FPS for 11 RAWs or 32 JPEGs
1D II - 8mp @ 8.3FPS for 20 RAWs or 40 JPEGs
D2x - 12mp @ 5FPS for 15 RAWs or 26 JPEGs AND
6.8mp @ 8FPS for 26 RAWs or 35 JPEGs
D2Hs - 4mp @ 8FPS for 40 RAWs or 50 JPEGs
Now personally, if I were a sports guy considering the 1DII and I owned Nikon glass, I would have to think long and hard about whether it was worth sacrificing 1.2mp, ~0.3FPS, 8 frames of buffer, and $800-$1000 extra for the versatility of ALSO having a 12.2mp 5FPS high res mode. Now if you're a current Canon shooter with an investment in Canon glass who will NEVER use the 12.2mp, the answer would probably be it's not worth $1000. However, as a Nikon shooter, you'd lose more than that extra $1000 switching out your lens system. Not to mention the fact that based on what forum you're on, I bet you will want to use that 12mp mode.
I know Canon is better at hiring dozens of reps and sending them to troll forums and talk up the evils and patheticness of Nikon at shooting events and tell you that their cameras are God and EVERYBODY has switched and you're a loser if you don't. I have a friend that fell for it. You shouldn't.
Go D2x, baby. I envy you, I wish I could afford to update my D1x.