I just received the new Mamiya adapter. The 40mm Distagon and 180mm Sonnar are excellent. But not better than the Mamiya 80mm, which is also excellent.
The 110mm is another story. Performance is poor. I'll have to look into it further. I don't see anything wrong with the lens, and it was fine with film (albeit over 10 years ago).
All in all, I don't think the Zeiss lenses (which I LOVE with film) are better than the Mamiya, and are certainly less convenient.