I'd certainly not get the 24-70mm L MK I, I had five and they were not worth the price. Finally, after hanging back for reviews of the new MK II version, mine arrived this afternoon. I already had my FoCal AFMA setup ready. The settings with a quick run were -1 at 70mm and +1 at 24mm.
The contrast was excellent, lending to the sharpness.
I hope to do a more careful analysis tomorrow.
I've owned two 7D's, two 5D MK II's and two 5D MK III's along with several 1 series. While the 7D AF is good, I found my 5D MK II to be a much better overall camera. Certainly it did not have bad AF.
If you want a excellent body for low cost, get a low usage 1D MK III. Its far better than my 7D's were, and is available for pretty low prices.