There is something about this lens that is hard to describe unless you've held it--it has a balance that just "feels right." The latest generation of stabilization, combined with its shortness, heft and balance, make it easy to handhold consistently at 1/60th sec., and often as slow as 1/30th sec. without any visible blur.
At 1:1 on a 30" monitor I don't see any chromatic aberration. This has become my standard "street" lens for walking around. Whether on a 5D MkII at 70-300mm, or on a 7D at 112-480mm, this lens has a great AF motor, and reacts quickly and decisively, despite the designer's need to trade off aperture speed for a hand holdable size.
Canon hit it out of the ballpark with this one. It is a bit pricey, but it's solid, sharp, slick, and doesn't compromise on making you feel you're holding an optical gem.