I've got this lens, and it's been pretty good. Images are a little softer than what I would like, but the IS does help when shooting slower shutter speeds. The price I last saw on Amazon.com for it was around $380, which is pretty good I think.
I use Photoshop a lot, so it's easy to go in there and sharpen the image if I need to, so that saves me as far as softness goes.
And the 17-55 mentioned is a great lens, and is indeed very sharp for a non-L lens. The trade off of course is the price, if you're comparing it to a 28-135.
In the end though, if you're looking for something in the focal length range of a 28-135, I would go back and settle on the 28-105 if I could choose again. Little bit sharper is what I have heard as well, plus the f/4.5 is a good bit better than f/5.6.