I bought this lens more than a year ago to be the primary walk-around lens for my Digital Rebel/300D, which I've since replaced with a 20D. The lens has worked marvelously on both bodies, offering extremely sharp performance to the borders at all focal lengths and maintaining sharpness well at wide apertures. CA is also not a problem at all and build construction is commendable. The inclusion of the lens hood and pouch further increase the value for the money.
I have, however, since switched over to using the Canon 17-85mm much more often. This is partly due to the fact that I missed the 17-24mm range more than I was using the 85-135mm range. In addition, Tamron's AF is somewhat slow and causes the focusing ring to move (which one does get used to). The lens is a bit heavy compared with the Canon, uses more expensive, larger diameter filters and is missing IS.
Contrast is great on both lenses, with the Tamron rendering slightly warmer colors.
Nevertheless, it's hard to fault this lens for the price and I plan to keep it in my arsenal for when I know my needs of the moment will be skewed more toward the tele end or in good lighting when I need the sharpest results.