I have use this lens for approximately a year and it's been on my 350D almost permanently. It was also the first lens I bought when I went to digital from my old Minolta...
After taking around 4000 pictures with it, I can say that the image quality is very good. Not quite at the same level as the L lenses I got after but, considering the price, how could I complain?
Image quality was good, no BT, colour was excellent. No complaints about the built quality or the glass.
However, this lens has a mind of it's own! It took some serious taking use to. The auto-focus is noisy and slow. It searches for focus in low light. That's why I took most of my low light pictures manually...
But like I said, at that price, you can't complain.
Considering that it costs about a quarter of an L F2.8,
it's a great lens for the price.