Ellis,
I tried the 90mm version. While extremely well-made and great optically, I chose to stick w/ the Nikon 85.
One thing I wanted it for, especially with the lens-mounted foot, was shift-stitching. In order to perform a left-center-right stitch, you have to loosen the clamp, rotate the lens 180˚, counter-rotate the camera, then re-tighten the clamp. In contrast, with the Nikon you shift left and shift right, counter-shifting the body in an A-S clamp.
The optical improvement wasn't enough to overcome the price and cumbersome use for me, YMMV.