10 out of 10 points and recommendedExtremely sharp, fast, and with great IS.Collects dust on internal elements.
I'm a pro who has shot tens of thousands of frames with this lens and I ABSOLUTELY LOVE IT. This is a fabulous general purpose zoom lens capable of top-quality professional grade results.reviewed October 22nd, 2007 (purchased for $999)
It performs especially well from f/4 through f/8. I usually have mine set at f/5.6 or f/8. Check the sharpness test here on SLRGear.com:
In fact, if you compare it to SLRGear's sharpness test of the EF-S 60mm Macro, at 55mm this zoom actually outperforms the macro.
However, it definitely DOES gather dust on the back surface of the front lens element group and the front surface of the second lens element group because the lens is not well-sealed. The good news is that it only takes a few minutes to remove the front lens group and clean the dust out.
By the way, the EF-S 17-85mm is prone to the same problem, and the fix is exactly the same for both lenses. Here is the abbreviated version of the cleaning process:
1) With the lens facing upward, carefully pry up and pop off the trim ring on the front of the lens. It's just a thin plastic ring held on by a permanently tacky adhesive.
2) Remove the three Phillips 00 screws that you find under the trim ring. Be sure to use a Phillips 00 size screwdriver or you may damage the screw heads.
3) Holding your hand over the front element, turn the lens over and the front element group will fall out in your palm.
4) Clean all exposed glass surfaces.
5) Reassemble in reverse order.
When I get a few minutes, I'll post a photo tutorial on my website, http://www.ashcreekimages.com,
showing how to do this very simple service.
I don't have a definitive comment on the flare issue that others have raised. I shoot primarily outdoors. I use the annoyingly overpriced lens hood or otherwise shade the lens to keep sunlight from falling directly on the front element, and I haven't experienced a flare problem.
However, if excessive dust accumulates on internal lens element surfaces, that COULD lead to flare.