<One caveat: when you are in a post processing program now, and look at a 1:1, bear in mind it's a very different 1:1 image than before. I think that's what is throwing a lot of people. Everywhere you see "this is a 100% crop", what they are saying is "this is X pixels". With twice the pixels for a given part of an image in each direction (+/-) this means in effect you are seeing a 2x magnification relative to a 1:1 image with your prior camera.>
This is an important point. I did a quick test in View NX2 with two images of the same scene at the same focal length with two different cameras - a D200 IR and a D7000. The D7000 image at 100% was tighter than the D200 reflecting the smaller sensor of the D200.
Here are the referenced images to confirm that a 100% crop varies by sensor size. The Color images are from the 16 mp D7000 and the B&W images are from a 10 mp D200.
EXIF is attached to the files. The settings are slightly different as these images were created for another purpose. But the crop demonstrates the difference in zooming at 100%.