Like many happy reviewers before, I'm very pleased with this lens. The focal range covers most general usage. The constant f2.8 aperture was one of the criteria I wanted in a lens.
Before this lens I owned a Sigma 15-30 and 24-70 f2.8. These were a lot of fun, but I got tired of having to carry around two lenses. Also, the image quality of the Sigma's wasn't always up to standard which made things very frustrating after coming home and reviewing the pictures and finding them not up to spec.
Anyhow, I sold the Sigma's and added a little extra cash to afford the 17-55. Overall I'm very pleased with the lens. The sharpness is superb over the entire focal range. Also, the added Image Stabilization (IS) allows sharp pictures with shutter speeds of 1/6 of a second taken from hand. That's something that no other lens does!
I would also recommend getting the hood for this lens and a quality UV or CP filter. The only downside to this lens is the overall weight. To me its acceptable because it is compensated by the IS, USM and f2.8.
The debated issue with the hood and other accessories not being included might be a little up tight considering the price of the lens. However Canon only includes these with their "L" series. Personally, it might be a little tight from Canon, but if you can afford this lens then the hood shouldn't be that much of a problem financially.
In short, if you're looking for a general purpose lens with high quality optics and fast performance this is the one to get! Sigma and Tamron offer similar optics (I've tested both), but these don't compare to the Canon.