I have the Hasselblad to Contax adaptor that Hasselblad made. Since I already had a Hasselblad system and a Contax 35mm SLR system, so it just made sence for me. I didn't have any longer Contax lenses and I did for the Hassy.
You don't need to cock the shutter every time you shoot it. You can't get the Hassy lens off the camera unless it is cocked and then when you put it on the adaptor there is no way for the camera to trip the shutter in the lens so it just remains open the whole time like any other lens used with a focal plane shutter camera. Just no automatic diaphragm control. The only thing about using the Hasselblad lenses on a 35mm SLR is that there is usually a smaller, lighter and faster option available for your camera.
My 85mm sonnar for the Contax is about the same size as my 50mm 1.4, but if I put my 80mm planar for the Hassy on the camera, it dwarfs the camera in size and mass, not to mention makes the camera very front heavy.