I have the same setup. AFD2 and Aptus17. It has not been trouble free, to say the least.
However I have been told there is a firmware update to the AFD2 that is supposed to solve a lot of the communication problems I have had. CAmera loosing connection to back, back not sensing camera etc. So make sure your camera has the latest firmware! or else you might end up rebooting more than taking pictures..
There is about 1.3 "crop factor" i think. Works fine execpt for interiors that I do a lot. The 35mm is not wide enough. But for most other situations it works fine.
as have been said, avoid ISO400 - useless. If you expose exactly where you want to be ISO200 is ok. Personally I like the iso100 a lot. ISO25 is VERY clean.. beautiful files..
I find that it renders blond hair often red or brown.. However that might just be me not using it correcly..
The amount of details and "clarity" of the files are very good. Being used to shooting Canon the last 4 years now almost every frame with the Aptus makes me go "wow".. It might be pixel-peeping.. but "wow" I do like the files, but download and try the software. You will most likely be spending a lot of time with it...
Most of the "Folk" images on my website are aptus. The party-series are all ISO200 if I remember correctly..
I'm considering a Leaf Aptus 17 back for my Mamiya 645 AFDll. I can't find any info on the lens conversion or a review that speaks to any noise issues. Help if you can.