I'd recommend the 17-50 lens, it'll be a lot more useful and you won't change lenses as often. The 17-35 is a left-over from the era when film cameras dominated the market; the corresponding lens in the dslr world has a focal length range of 10/12-22/24.
It also works on film cameras and FF sensors -- although I can't imagine that someone shells out $3k on a Canon 5D and then buys such a cheap lens.
My point is that this lens is mainly aimed at people with analog (read: film) bodies who also want to use it on their digital body. The `Di' moinker is marketing speech for `designed with digital cameras in mind'; usually that means it only works on dslrs.
However, my main argument remains: that particular focal range is definitely not appealing for someone with a dslr. Either take a 12-24 zoom or 17-50.