I upgraded from the 5D to the 5D Mark II and I haven't noticed any significant change in general IQ either then the increased resolution. Which is nice to have, but not all the time. What impressed me is the LCD screen, I know it is the same as the one on the 50D but I feel it is different. The 50D brightness settings are a bit strange, sometimes too dark or bright, hard for me to find a good setting. Live View and Movie Mode is a nice addition, also not necessary but one of those "nice to have" features. The sensor cleaning is an obvious upgrade, don't know if it really does anything but I hope to think it does. As for the micro adjustment, I don't use it (fortunately). My lenses are all focusing like they should. I went through an in depth check a while back with all my lenses and they all passed the focus test =D. I think if you don't mind the LCD on the 5D, it would probably be a better buy. With the prices of second hand 5D bodies dropping, you could save quite a bit. The difference between a brand new 5D and 5D Mark II is small, so if you are thinking about buying a brand new 5D, then maybe you should just get the 5D Mark II. All in all I enjoy my new 5D II, it offers great IQ much like my original 5D, except now it has all the new features of 2008/9. But If I were you, I would get the 5D and with the money I save get a lens you want =D.