DxOmark tested the Sigma 18-35mm f/1.8 DC HSM A lens for Canon mount ($799) and labeled it as the "best performing APS-C zoom":
"With the introduction of this model, Sigma has the best performing zoom of its type. The DxOMark score of 25 points puts well ahead of both the full-frame Canon EF 24-70mm f/2.8 L II USM and the Tamron SP 24-70mm f/2.8 Di VC USD (though bear in mind those lenses become the equivalent to a 38-112mm on a Canon APS-C body)."
Here are few comparisons between the Sigma 18-35mm f/1.8 and other lenses (even some primes):
Check also the latest rebates on Sigma products:
