I forgot to mention that I do own the 17-55mm F2.8 DX. It's a fantastic lens. =)
Of course... it's not very useful to me anymore now that I'm using FX.
The DoF for F4 on full frame looks about F2.8 on a cropped body, as a side note.
It's worth considering the following instead of the 16-35mm (all with their own adv./disadv.):
1. Similar primes