... But I just found that, with that dark viewfinder in the Contax 645, and with the max Fstop of the Hartbleis, they were VERY hard to focus, even not tilted or shifted. (Remember too -- it's Manual Focus only).
I guess the 45 tilt shift on the Mamiya will be similar.
I think this a big difference between trying to do this type of work on MF or on 35mm than with a view camera. While little about using a 4x5 view camera is easy, the large ground glass and a focusing magnifier make to possible to tilt and check focus very accurately. And if you are using a Sinar or some other advanced cameras there are simple methods to use the scale on the focusing mechanism to transfer the tilt values to the lens and back standards. E.g. you focus on one spot, set the focusing scale to zero, focus on the other spot, note the value on the focusing scale, then you tilt the lens the same amount. There are vertical and horizontal lines on the ground glass that are used as specific locations for focusing.
Now that many 35mm cameras have Live View, it is possible to check the focus at a 10x magnification. Prior to that it was very hard for me to see the result of any tilt and focusing effect through the viewfinder - even with the brighter Canon lenses. However, one reason I went with the Canon 45mm lens over the Hartblei lens was that I mostly need shift, not tilt, the lens is f2.8 and it has an electronic aperture so viewing is at full aperture. The MF lenses are much bigger and heavier and the SuperRotator feature was not so important to me. Anyway the new Canon 24 and 17 have independent rotation for shift and tilt so it probably won't be long before they have 45mm and 90mm versions that also do that.