This is a very good lens. I just opened it yesterday and I won't go as far as to say I am thrilled, but I am very encouraged. The first thing that strikes you about the lens is the build quality.
Fast; accurate focus; Best built EF-S lens to date; No lens creep - YEAH; Center sharpness; Its aesthetically a good looking lens; Very useful zoom range; CAs seem to be well controlled
Only 3.5 at its widest and drops to 5.6 as you zoom; Wish it were 2.8 for most of the range, but I tend to think the cost would have been prohibitive for an EF-S lens, If you use the lens indoors and want fast photos, you'll need a flash, you'll need a hot shoe flash to minimize the vignetting at...