I'm finding this discussion extremely interesting. I'm 100% amateur, recently started doing some medium format film and have a grdII.
Tried to post something about this in
http://forum.getdpi.com/forum/showthread.php?t=7769 , which got ignored, probably understandably, as it was a somewhat confused post.
To cut a long story short. I ended up measuring the grey level percentages throughout the dynamic range of the GRD II, and for all iso values, in conjunction with the Aperture default B&W conversion. So now I know very precisely what to expect, and where I can go from there in with Aperture. Also appreciate the massive differences between film and digital, and the essential uselessness of the default metering decisions (I'm sure this is A LOT better in the sony).
Enjoying my photography a lot more since. Should also mention that the inspiration to do the above came after reading the Ansel Adams books, and write down a zone system for the GRDII
Anyhow, was glad to read all the informative posts in this thread.