Acquired my new lens on Thursday. I have been shooting it back to back with my 24-105 (purchased in Feb. of 2012) and I just don't see a real difference. Perhaps slightly sharper and slightly better contrast but nothing that would put a big smile on your face. Nothing that changes my overall impression or enjoyment of the image. Perhaps I have a bad copy of the 24-70 or an exceptionally good copy of the 24-105 (or some combination therein). I will go out again but I know that I have already decided to return it. A nice lens but the extra stop is not worth the loss of range and IS (not to mention $2,300 when a good filter is included). Disappointed as I was really looking forward to using it and enjoying an appreciable jump in IQ. PS - All images viewed on a calibrated Eizo ColorEdge.