Hi all. Sorry for the longish response to follow concerning this subject: Remember as you read this that I have and use all the gear being discussed and then some ...
The notion of "horses for courses" is exactly right when drawing a comparison.
Yes, I do take quality images with my 1DsMKII ... when using it in spontaneous or action oriented situations like those at a wedding, sports etc. The Canon is a great DSLR ... it's fast ... but so are lesser priced DSLRs that would provide image quality up to standards needed for this type of work.
What has confused the issue is internet chatter that the Canon 1DsMKII is able to challenge Medium Format in terms of image quality (the "s" was originally meant to mean "studio"). IMO, this is a fairy tale propagated by either those who have invested in the $7,000 to $8,000. Canon and are defending that decision, or are partially blind.
There is a reason studio shooters are using these MF digital backs ... even the 16 meg ones like the old Kodak Pro-back, the 96C or now this CFV.
I have not, nor ever would use the Canon for a commercial application while I have a MF digital back available. Neither would my pals who shoot commercial work, or for that matter any photographer I would hire to shoot an ad layout for me (I am a Creative Director for an ad agency BTW). The exception would be an idea requiring the spontaneity or action oriented attributes the DSLR would provide.
Here are some the reasons:
Meg count isn't everything when it comes to digital capture. The Canon is the same meg count as the CFV, but the space that meg count is crammed into is considerably different.
The CFV pixels are much larger, which translates into smoother tonal transitions.
The Canon is 12 bit where the CFV is 16 bit ... more data going in.
The Canon is a CMOS sensor with a filter ... the CFV uses a CCD with no filter. IMO, the CFV images are more life like and less plastic looking as a result. On the other hand the 1DsMKII can be shot at much higher ISOs.
It really comes down to what you like to shoot, how you shoot, and what your personal criteria is for image quality. If you like to photograph the kids at play or street photography
then a DSLR is your best choice for the most part because it's attributes better align themselves with the purpose you have in mind. But I would say the 1DsMKII is overkill for that sort of application.