Not sure where some of this information is coming from?
Regarding "Bokeh" ... the issue with MFD isn't lack of it as suggested, it is that MF has a shallower DOF than 35mm and you have to be careful about what is in focus or not. Every MFD system has it's fast optics: Hasselblad HC-100/2.2, Leica S-100/2 and 120/2.5, Contax 80/2, and there's even some f/1.8 lenses ... I'm sure Phase One has their's also. I've shot a HC100/2.2 on a H4D/40 next to the legendary Leica M75/1.4 and the DOF/Bokeh was almost identical.
Regarding shooting a group with and without lights ... the comment about black backgrounds simply illustrates lack of knowledge in the use of lighting. Background exposure is controlled by shutter speed ... using what is called "dragging the shutter", you can open up the background exposure while the strobes illuminate the foreground and flash duration freezes any subject movement. Using high sync speeds in low light is a common amateur wedding photographer's mistake. This principle is the same for any format.
Regarding the High ISO performance Greg asked about: the comparison demo Voitshatter posted only illustrates my previous point ... all the samples are different degrees of ugly. The point of photography is to find the best light, not the worst. Technically, 35mm CMOS does allow more latitude in lower light, but poor light is still ugly ... and 90% of the time it is poor at an indoor wedding reception.
The point is that why should
poor light be the driver of a gear decision, when there are
good light solutions?
Regarding operational speed:
Decisive Moment type wedding images happen to be my modest claim to fame. My tag line is "Romantic Photojournalism". However, I did quickly learn that fashion and portrait was also important to be successful in my market. So, I use a rangefinder and DSLR for the candid work, and a MFD for the fashion/portrait/group images (and available light candid work outdoors) ... which BTW are what sells. I get the job because of my humanistic insights and treasured moments, but make after-shoot money from the more structured work with MFD ... which is what pays for all this stuff
They are also the images that tend to be printed larger than the candids: 16X20 in albums and even larger to be framed.
Interestingly, I get as many or more insightful keeper candids with the manual focus rangefinder than the lightening quick AF DSLRs. The secret is ... anticipation over reaction.
Here are a few images from one casual type wedding shot with a S2 and MM rangefinder. All the shots attached were MFD, and all but the group image were shot at ISO640 to keep the shutter speed up and the DOF narrow (now ISO800 on my newer CCD camera). Most with just a puff of fill flash. Note the narrow DOF on a few of them illustrating my "Bokeh" point above.
A good DSLR and MFD is a dream team for weddings IMHO and long experience. Use them for their respective strengths and they compliment each other perfectly.
- Marc