I've had my eye on the Canon EF-S 15-85mm Zoom Lens for the Rebel T1i that I carry for casual assignments. It seems like a substantial upgrade to the kit 17-55mm lens, but at a price: about $725 US. Before making such an investment, I want to know all the ins and outs of this handsome chunk of glass.
Fortunately, the good folks over at CameraLabs.com have posted an excellent video review of this zoom, accompanied by a full written report about its performance.
If you've been considering this zoom for your Canon 7D, 50D, or Rebel, you might want to take a look at the CameraLabs report. They give it a very favorable review, with some helpful insights about its hands-on usage.