I've been considering the Sigma 15-30mm EX for a while. I'll consider the Sigma 17-35 once I see user reviews. I think Sigma is coming out with a 12-24mm (availability)in the next few weeks.
Actually, I should say that yes there are versions of the 17-35mm available but the one in the dpreview article isn't the one being sold on the B&H website.
It appears the DG version is an update to the HSM focusing, giving you the same "manual override" of AF by twisting the focus ring as what the Canon "USM" lenses provide.
Q: Some Sigma lenses are designated "DG". What does this mean?
A: The DG designation applied to certain newer Sigma lenses (mostly wideangle and wide zoom type lenses) indicates that the lens is especially suited for use with digital SLR cameras. The DG lenses feature improved (more even) light distribution from image center to edge, especially at maximum aperture, compared to conventional fast wideangle lenses.
Sigma's HSM is their version of Canon's USM, both of which allow full-time manual focus (for those Canon lenses with ring-type USM).
