Fact of life: fast lenses are expensive, and fast zoom lenses are expensive and heavy. While we can't do anything about its bulk, as long as Sigma's $799 price for its 18-35mm f1.8 doesn't rise to the $1,160 currently in strikethrough type on Sigma's Web site, this lens will remain a great bargain for serious photographers shooting with an APS-C camera.
The lens, which bears Sigma's "A" branding for its arty lenses -- marketing-speak for wide-aperture -- has the same excellent build quality as its 35mm f1.4 full-frame lens (which, at a current price of $899, is also a great deal). It uses all-metal construction with well-damped, rubberized focus and zoom rings and an easy-to-feel and operate focus mode switch.
Yes, it's heavy, but I love the feel of Sigma's A series lenses. It overbalances light cameras like the Rebel series a bit, but are a great match for the slightly heftier EOS models like the 60D (and the forthcoming 70D) as well as the 7D.
It's not a particularly feature-rich lens -- aside from the manual/auto focus switch there's a distance readout window for the manual focus and focal-length indicators for the zoom ring, but that's about it. I know it's rare to have optical image stabilization in wide-angle lenses (and many manufacturers will tell you it's unnecessary), but I really would like it. If you shoot video without a rig, it's essential. Of course, this isn't an issue for Sony bodies that use sensor-shift stabilization. It's also supported by Sigma's optional USB dock, which allows you to manage and configure lenses and firmware updates.