Why not add my 2 cents to the other 217 reviews?
I bought this lens 2.5 years ago when $425 was a screaming deal and was overall fairly pleased. I used it extensively for 2 years before selling it.
I found images very sharp on the long end, especially when stopped down one stop, but even at 5.6 I found it quite sharp. The IS was extremely valuable, as I was often hand holding in marginal conditions.
All the bad things people say about performance on the wide end I also found true...CA, distortion, soft. The distortion was a problem for me because many many of my images had a water horizon low in the frame. I think many people could happily use this lens at 17mm and not notice the distortion.
I paired this with a 10-22, which is fantastically sharp wide, so I only used 17mm when I couldn't change lenses or when it was dark and IS was badly needed. Pairing these two lenses makes a very light weight kit and avoids many of the failings of the 17-85.
For a general lens I think this would please many people, and at current used prices of $350 or even $300 or below, I think it is a very good value. Right now my shooting doesn't require a small, portable walk-around lens, but if/when it does I would buy another.