I was overwhelmingly surprised by the 5D. It revolutionized my shooting. For the past decade I was tripod bound with the RZ, which I downsized from a behemoth Fuji GX680! Yes it has it's limitations, and in some areas it can't compete with the RZ and film but really those differences are overshadowed by what shooting digitally bought to my my work.
Most of my work is editorial and printed no bigger than double page. Double page doesn't quite compete but it still looks good. Single page is marvelous. It works just fine and I've never in 6 or so years had a complaint.
I miss the result of film. But I don't miss the time it takes, the trips to the Lab, the waiting, returning bad scans, the countless hours of spotting dust...
As for sharpness, Im often adding .5 pixel gaussian blur to the 5D, so really, I don't need any more. I can understand if it is your job to accurately render reality that you'd want the sharpest possible tool, but for me that isn't a consideration. And is there really that much a difference in a real world print at 10x8, 11x14 between the sharpest and what I have? No I doubt it.
While there's a good chance I wont use the RZ again, I wouldn't sell it. That camera and I went places! So now it sits in it's case like time forgot it.
I made the move from an RZ Portra and Provia system about 6 years ago, which I thought I'd never do. When the 5d came along I bought it to play with, I was that impressed by it that I'm still using it today.
How do you find the 5D as compared with the rz system? I have an rz system I can't justify keeping, but it's hard to get rid of. I just like the feel of it.
I just upgraded from a rebel xt to a t2i. I wish I could say the image quality and finder are significantly better, but they're not. Higher ISOs and live view are nice, however.