So I picked up my 5d Mark 2 the day it came out and have been very pleased so far. Here is a test shot I did of my brother-in-law as we were preparing to shoot his senior pics - since he was making "big eyes" it showed off his eye detail nicely. I cropped down the image at 100% so you could see the level of detail it is capturing, even at a decent distance from the subject. First, the original image for a "distance from subject" reference - this shot is straight out of the camera except for a slight exposure bump.
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Now here is the 100% crop of his eyes - this is straight out of the camera with a Sharpening Amount setting of 25
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Here is the Sharpening Amount at 75 with no masking
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Now a setting of 100 with no masking:
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Now a setting of 150 with no masking!
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And finally, I added a Masking setting of 70 with the Amount still set at 150
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Of course these are lossy jpeg images, but hopefully you get an idea of what this camera is capable of. I couldn't get this amount of eye detail with my old 10D using a macro lens! I wish I would have shot some with my 5D for comparison, but I am sure that with 75% more megapixels the Mark 2 would definitely outshine it, especially when you consider how well the Mark 2 held up to sharpening.
I hope to post some high ISO comparison images soon as I was very impressed with this camera at iso3200.