9 out of 10 points and recommendedSharp even at f/2.8, improves quickly one and two stops downFocus not as fast as USM, buzzing noise when focusing,no full-time manual focus or IS
I bought this lens with a new 30D as a general use walkaround and for people shots. I've been ver impressed with it so far as there is excellent detail in the centre even at f/2.8 iso 1600 in challenging lighting conditions.reviewed January 4th, 2007 (purchased for $490)
Sharpness does improve quite a bit when stopped down, I find for group shots f/5.0 gives good results.
On the downside, the distortion at the wide angle (17mm) is fairly dramatic at the edge of the frame. It's not too hard to correct in processing, but I find myself framing shots so that no-one's face is close to the edge when at 17mm which reduces the effective range a bit. However, it's good to have it for those times when you absolutely have to go wide.
Some posters commented on the loud focus noise and speed. While it's not as fast or smooth to focus as my 85 1.8, it's perfectly acceptable for general use and I haven't missed any shots because of it, in fact I've caught a fair few reaction shots at events. It wouldn't be ideal for sports but then a 17-50 f/2.8 zoom isn't a sport shooter's chocie anyway.
There is a buzzing noise when focusing but it's not that loud. It's no more disturbing than the 30D's shutter anyway.
Overall, I'm very happy with the lens!