While I'm not a Canon shooter, I have to tell you that I have friends who are, and the consensus I hear from them is that the 50D is a waste of plastic. The talk I hear is that the image processing isn't as good as older gen stuff, and that skipping this camera is your best bet. What I hear of the 5D, well, my choice would be to go for a low shutter actuation number and have a blast. Not being a Canon shooter I can't tell you how to find the shutter actuation number, but try to figure out how to check the total number and go with a low number 5D.

I would skip a used 5d and go for new 5D Mark II if you can afford one. Full frame Canon requires Full Frame lens EF lenses without EF-S designation.

I've been happy with the 5D except that they should have kept the way they number the folders in the 20D. We had a 20D at my job and it finally broke after 3 years of continuous use. Other than small buffer size, I would had prefer a larger buffer, I find the buffer fills up quickly, even for non- sport photography.

The 5d is better at low light than compared with the 20 D. I never owned, the 30D, 40 D or the 50D. In about a year or so they will fix any bugs hopefully in the 5D Mark II, and used 5D will probably be had on the cheaper side. We are in a recession so I would think photogs needing cash for their used gear will dump them.