The EF-S lens that has had some full frame users jealous for a while.
Not the educated ones, who would know that the EF-S 17-55mm f/2.8 IS on a crop body is out-spec'd by the EF 24-105mm f/4L IS used on FF, since the FF-equivalent of 17-55mm f/2.8 is 27-88mm f/4.5 (becuase the crop factor affects aperture in terms of DoF for equivalent framing), and the 1-stop effect on shutter speed is more than compensated for bu the 1.33-stop improvement in ISO noise with the additional light gathering ability of a FF sensor). So, the 24-105 on FF is wider, longer, and faster than the 17-55mm on crop, still has IS, and is weather-sealed with L-quality build to match.
Having said that, the EF-S 17-55mm f/2.8 lens is, IMO, the best general purpose zoom for a crop body (although the EF-S 15-85mm f/3.5-5.6 IS is a good alternative for outdoor use where losing 1-2 stops of light is tolerable).
Here are a few of my shots with the 17-55mm:
EOS 7D, EF-S 17-55mm f/2.8 IS USM @ 17mm, 1/3 s, f/22, ISO 100
EOS 7D, EF-S 17-55mm f/2.8 IS USM @ 55mm, 1/2 s, f/13, ISO 100
Rebel T1i, EF-S 17-55mm f/2.8 IS USM, zooming during exposure, 1/20 s, f/22, ISO 100
Thanks for looking!