I owned the 1st 24-70 f/2.8, I believe I had a softer sample as they had quite a range of variation in them, however this version is loads better. It is almost as sharp as my macro, even wide open, which is unheard of for a zoom.
Sharp; Fast AF; Excellent General purpose and portrait lens; weather resistant
Price; though its worth it in my opinion; filter size makes for expensive filters