I borrowed one from Marcel a while ago to use on a trip to Newcastle, used it on a 350D. I was gobsmacked by the quality of the images even on that camera!
My longing became a reality last year and I bought one. Love it to bits and it is rarely of my camera, which is now a 40D, bought to get the best out of the lens.
The quality is everything that everyone has said about it. I had a guy drooling over it yesterday in the peak district, on top of Shuttlingsloe, he asked to see the images on the screen and went away mumbling, 'must get one, must get one'!
Prices are really good at the mo, and you won't loose much, if and when you decide to sell it!
Go for it!