FWIW, just got my Mamiya and have been playing around with a few lenses. I only have the ZD back at this time, but here's what I can tell you...
My 110 Planar absolutely rocks (second generation F lens), and this is at just about any aperture, even wide open. The Mamiya 200/2.8 APO MF lens is in this league too --- both are stunningly sharp. The 200 negative is it only focuses to 2.5 meters, but it's cheap used. The 110 Planar of course focuses close, to about .75 meter and is NOT cheap.
Going to be testing the 80/2.8 AF directly against the manual focus 80/1.9 later today, but initial images show the 1.9 is superior. I'll report back with my final findings...
The 35 AF and 55-110 AF are both pretty good, but not in the league of the lenses above. To clarify, I'd say the zoom is about as good resolution and distortion as the Canon 24-70/2.8, and the 35 is about as good as the Canon 24 L, so they're good, but not stunning. I would agree with Edmund on the 80 AF as well, and say that these lenses are *not* out-resolving my 22MP back. While I have not done an empirical test to confirm this, my logic is the 110 Planar and 200 APO look so much sharper they probably are out-resolving my sensor. The 80/1.9 may be close, more later...
Have a 50 Planar coming this week so will report back on it...
As an aside, I picked up a scrungy 145 Soft Focus Mamiya. This lens was really cheap, under $100, because it had fungus. I have it at the shop getting cleaned. This will prolly cost me over $200 to get that done right, but still not much invested for a special-use glass. Anyway, I snuck a few shots off before sending it out for the CLA and it looks really promising for say artistic portraiture or still-life, figure, etc... Way nicer effect than any SF filter or CS treatments.
One of the huge benefits of owning a Mamiya system is the range of glass you can mount on it. The other is the fact the FP shutter goes to 1/4000th, so I can actually shoot a lens like the 110 f2 Planar wide open in daylight without having to add an ND filter...
More later!