Many on here rave about the sharpness, lack of artifacts, and colour of the Sigma Merrill / Quatro. A multi shot medium format camera / back is like a Merrill/Quatro on super steroids. Multi shot was created for a fully locked down camera studio tethered shooting situation. However I have shot it on location outdoors numerous times. Also a totally different budget level though to a Merrill.
The big negative has been the live view quality. I own a H3Dll 39ms, have owned a 528C, and shot the 50ms and 200ms. The LV on all those backs is VERY LOW GRADE, and that is being very polite. There has been no real improvement from the 528C through to the H5 versions. So some REAL improvement via CMOS would be wonderful.
If the new 50C ms CMOS version comes out with LV comparable to Nikon or Canon I will jump right on one. Even if it is only available tethered. After all multi shot is only available tethered.