Maybe its me or maybe my copy of this lens is very good, but I find it funny that so many of the members here say that so-and-so lens is soft at the edge, or soft at f/2 or f/16 etc etc etc. I don't know, for my money my lens produces pretty darn good 13" X 19" enlargements, as long as I don't severely crop enlarging the pixels unacceptably from my D7000. I don't plan on replacing this lens due to lousy optics, because I don't think "my copy" is inferior. In fact, I was hard pressed to tell the difference between uncropped images from my lens and the 70-200mm f/2.8 at the same aperture, certainly not worth $2000 difference. And its sooo light and easy to use as an everything lens.
Why persons continue to pixel peep to reveal lens optics faults, I have stopped doing it myself (I used to do it too, a bit), I'll never know. Nobody views images at such magnification anyway. Enlargements are viewed from a distance are not meant to be examined close up, any more that famous painting are.
And besides, as has been said many times, and I tend to agree, that most of the quality of an image has more to do with the imagination of the photographer than his equipment, as long as he/she knows the limitation of that equipment.