Hi James!
The lens is indeed a medium format lens. It's just several hundred dollars cheaper than a Canon version, is APO, and very sharp. It is attached to my EOS bodies with a mechanical adapter, in this case purchased from Fotodiox. The lens has a built in hood with an aadditional accessory hood that screws onto that. Beside from the fact that it is very sharp, I like the tonal range it shows for colors as it tends not to be so contrasty that it blocks up the shadows. It seems to handle this much like most of the Leica R lenses I also adapt to my DSLRs.
Basically you control the aperture via the ring on the lens and use you DSLR in either aperture priority or manual mode. TTL metering is pretty accurate with this lens. The only real drawback for me is that it is a very front heavy lens without a tripod mount on it.

This is a sample of what it can do. I find a real nice feel to the way it's rendered the yellow in this shot.