By contributing editor Chuck Fadely in New York:
Sigma is aiming high with their new 24-105mm F4 DG (OS)* HSM | Art lens for full-frame cameras. They promise higher image quality and less falloff than similar competing lenses. They set pricing at $899 after we talked to them at PhotoPlus Expo. The lens is a constant aperture f/4.0 but does not hold focus during zooming. We also looked at the 18-35mm f/1.8 zoom for APS-C cameras, which does hold focus.
More info on Sigma’s site.