After reading up on it, don't bother. It's a different sensor with a different image processor and the same old AF system. updated lcd screen, etc... Canon pretty much put a few new things into a 3-4 year old camera. I was really excited at first but feel a tad let down by Canon. D700 is in my future as it's the better camera for a couple hundred more and I won't have to switch systems.
The only real thing the 5DMK2 might top out on is IQ and the detail of the extra megapixels.
Then it's a shitty style. If I want to look at an abstract, I will look at an abstract, not a poorly post processed image that looks horrible. Yes, I'm a snob.
They did more than to toss a couple things into an old camera.
Brand new sensor.
3" High res LCD
Auto light Optimizer/Highlight tone priority
Live View (Silent shooting mode)
New battery technology (30% longer life w/ much more accurate life indicator)
Better weather sealing
HD movie mode
The AF works off the same system however its been tweaked to be more responsive/accurate.
Its going to be a ridiculously amazing camera. Its a major update, the ONLY thing I think they could have done to blow everyones mind is put in pro AF, but its not really necessary. And if you dont wanna shoot 21MP, you can just shoot sRAW @ 10MP.
Personally, I'll be picking up a 5D classic soon enough... but mostly because I simply can't afford the new one while im in school and job-less.