Though there are seems to be a lot of people using this combination, I haven't found many discussions or photographs on the topic.
I've added to my photographic arsenal a Fotodiox Hasselblad-EOS adapter, sold on ebay. This particular adapter has a tripod mount, which helps balancing the system when longer lenses are used. It doesn't have a chip, so the only metering mode available is center-weight average, and there's no focus confirmation. My Hasselblad set consists of the CF 50mm f/4.0 FLE, CF 80mm f/2.8 and CF 180mm f/4.0.
I use live-view for focusing and metering. A sturdy tripod is recommended, as a magnified live-view with a tele lens show a lot of camera shake. Though not necessary, I set the lens to F mode, disengaging the leaf shutter. Lens is stopped down through the DOF preview lever, and aperture is set on the ring. Image is clear and bright up until f/11 on the OVF, though some people might not want to go that far. There is a bug with the 5D Mark II that when in live-view and M mode, the displayed image is clearly darker than the captured photograph. The bug goes away if live-view is set to Movie and Stills, but then you lose all speeds below 1/30s. Av and Tv modes don't exhibit this problem, and I set proper exposure through exposure compensation dial.
On a subjetive analysis, it seems that it's a myth that these lens, made for 6x6, aren't capable of matching the resolution needed by these small and dense sensors. The 180mm is by far the sharpest and aberration-free lens I've used with the 5D Mark II, even wide open. It has been my favorite combo.
The 80mm is also a pleasure to use, and has very good resolution starting at f/4.0. I've tested the CF 50mm and the Canon 50mm f/1.4 side-by-side, and though there are subtle differences, they are hard to describe. The Hasselblad has a narrower field-of-view though.
From what I've seen, these Carl Zeiss lenses have excellent micro-contrast and resolution characteristics, though with lower global contrast. The result is low contrast and very defined scenes, very good for post-processing. And though some people may dislike, I find the pentagonal bokeh beautiful, an irreproducible characteristic of this set.
Here are some images (click for larger version):
CF 180mm with extensive perspective correction in Photoshop:
CF 180mm the first two, CF 80mm the third:
CF 180mm, handheld under rain: