I just purchased an EOS 1Ds Mark II, and the 24-70mm L lens. Needless to say I'm very happy. However, I've noticed that the sensor is sharper than the lens. There is a 2-3 pixel blurriness at 100% magnification (BTW: this is equiv to 56"x37" print). I have experimented with numerous F stops, to find the optimal, but the sharpness issue persists.
I do a lot of 4x5 copy work of paintings etc., and I'm convinced this camera can replace my 4x5 for my needs. However, I need a non-zoom lens that pushes the 1DS MkII sensor to the wall in sharpness. It also must have good chromatic characterisitcs and a very flat focal field. It doesn't need to be fast, or have wiz-bang electronic features.