The survey doesn't let me check multiple boxes - here's what I see...
Awesome improvement in AF
Significant improvement in frame rate
improvement in high ISO performance, which works well with the new AF
Improvement in white balance
Improvement in metering
More functionality
Interestingly, when I bought the original 5D, I made it a point to carefully compare it to the 1D2 that I had before. With the 5D2, I carefully compared it to the 5D. With the 5D3, I took a few hundred shots, and immediately sold the Mk II - not because it's a bad camera, but because the Mk III just impressed me in use. I never really took the time to do the one-on-one comparison. I was that happy with the III.