I use the ZF 100mm on a Nikon D3 since three months and find it to be stellar!
Unfortunately, I cannot compare it to any Canon lenses, but have compared it to the newest Nikon AF-S 60mm Micro, which is a fine lens, too:
The Zeiss is sharp wide open to the corners (fullframe) already with only little vignetting (which is easy to remove in post), sharpness and contrast increase slightly stopping down to 2,8. But certainly from F4 to f11 (diffraction limit on D3) the results are fabulous.
If you don't mind setting the aperture and distance manually, you'll enjoy using this lens in practice a lot: it's an exceptionally fine piece of engineering!
On the Zeiss homepage www.zeiss.com
you can find detailed information, including charts for MTF, distortion (which is minimal!) and vignetting on all the ZF lenses.
I also just purchased the Zeiss ZF 2,0/28mm with comparably great results. With the 28mm, curvature of field wide open can be an issue, as described in the excellent review by http://www.diglloyd.com/
There, he actually also compares the ZF 100mm to the Canon EF 100mm macro, with the simple conclusion "it couldn’t hold a candle to the 100mm Makro-Planar".
I'm absolutely sure it's resolution power will be sufficent for the upcoming Nikon 24MP D3x whatever.