Here's one from our forum's
own Mike Kobal.
Here's a review of the lens on cropped bodies
and another of the lens on full-frame
bodies. The consensus seems to be that the lens works great on DX bodies but not so well on FX bodies. On full frame bodies, the Sigma is softer than the Nikon up until f/5.6. At that point, the Sigma appears match the Nikon and occasionally beat it (at 70mm). Not too shabby for a lens that's half the price of the Nikon.
Having shot with the lens on a Canon 50D, I must say that I've got no complaints. It focuses fast, seemed fairly accurate and basically did what it says on the tin.