I have the EF-S 17-55 F2.8 IS as well as the EF 17-40 F4 L and EF 24-70 F2.8 L and between the 3 on a 1.6x crop body, I'd say the 17-55 is by far the most versatile. Image quality wise the 17-55 is also tack sharp wide open at any focal length. Colour and contrast is also very good (though I think it loses out to the 24-70 by a bit). The IS is surprisingly very useful even on the short focal length. Only downside is the build quality. The barrel is plastic and the focusing ring is a joke. The L lenses feel much nicer to use.
If you don't intend to upgrade to full-frame in the future or will be keeping ur 1.6x crop cam as a backup after upgrading, I'd say that the 17-55 is a very good buy.
