I just ordered a Canon 60d body and am now trying to figure out what lens I should get. I have around $500 to spend on a lens right now and will prolly add some more lenses in the future, but am looking for a single lens to use right now for shooting mainly video and some stills. Right now I am leaning towards a Tamron 17-50mm f/2.8
Seeing how the tamron is less than half the price, faster, and has a larger range, for a crop video DSLR i think the tamron 17-50 is the best choice. The canon 17-40 is a nice UWA for a full frame camera, but for 750 its just not worth it for a crop IMO.
Because the 17-40 is a full frame camera, making it a 27-64 f4 on a crop sensor. It's not absolutely useless, but its not an optimal range either, especially considering the fact that its slower and more expensive than the alternative.