Incremental increases over the version 1 lens - mild improvements in sharpness and distortion with a definite improvement in IS (4 stop vs old 3 stop). It's a bit heavier and a bit larger than the version 1 lens and overall feels more rugged (closer to the 24-70II). Sharpness is slightly behind 24-70II levels, but a definite improvement over my version 1 lens. The IS to me is night and day. I have gotten useable pictures hand held at 1/30 at 105mm with no problem. For my intended uses, this lens is hard to beat.