I have not had this lens for long but I am quite impressed with it. Focussing seems accurate with limited testing and colors/sharpness are great.
It has a good weight and seems to balance well on my 300D camera. I am replacing the kit lens with this one and it is a marked improvement.
I find it gives a good range to be paired with my Canon 70-200 F4 L.
I noticed that the lens is not quite 50mm at the telephoto end when compared to my 50mm prime, but it is close enough. It is probably closer to 48mm/49mm.
The only things that they could of really improved on this design was to fix the lens cap so that it could be removed without having to take the lens hood off. Also to use the HSM, but the focus is pretty speedy and not that loud.