Interesting discussion, I'm enjoying it. I've got a Contax 645, Cambo Wide DS (w/ P25) and a 5D. They all have very different looks to them, I'd hate to be limited to just one, particularly the 5D. When it comes to perspective control, I've tried most of the Canon solutions, and let me tell you, nothing comes close to large format lenses and a digital back. Like the Brits say, horses for courses....
On a side note, in the last 2 weeks, I've been on 2 different jobs where the art director (2 different art directors) pulled out a 5D and started taking snaps to evaluate composition, etc. Sure was glad I could pull out something a little more "professional" looking.