Finally got around to using Focal today. The first problem was finding a USB cable for the D7100. I knew I had one at one point for the D7000 but all the cables I had in the house were not the correct one. I ended up having to go to Radio Shack and buying one. For your info there are two different Mini USB-B cable ends. The one for the D7100 is a 8 pin . Not sure what the other Mini USB-B is but the ends are different.
Setup is easy once you follow the directions. With Nikon you do have to change the AF Fine Tune many times during the tests since the software can not change it for you but this is just a minor thing. IT is interesting how it does it. It shoots how it is now and shows in in one window. Then if has you set the AF Fine Tune at -20, -10 0 +10 +20 and then it will have you set at different points based on what the curve shows. IT will finally give yoiu a number to set in the camera and show you the results in a side by side comparison.
I tested 2 cameras (Out of 15 that you can test on the 1 license) On the D7100 I was dead on with the 18-140. The 70-300 was off by a few points so will see how it looks in the field in a few minutes when I go out shooting downtown. The D7000 only shoots with a 18-200 and it was off by several points so we will see how it looks after my wife shoots it this weekend when we go to the beach.
My final verdict is that I think it is worth the money and effort for fine tuning your lenses.
If you have fellow shooters in the area and you don't have 15 cameras you might offer to fine tune there for them.