Should work great. I don't know why it wouldn't. I used a Sigma 300/2.8 HSM with my Canon 5d Mk1 for awhile and though I finally sold it I had no problems. Some people have reported front focusing issues with Sigma but I suspect those problems can probably be corrected if they occur. Besides, you wouldn't know until you try.
Just a quick note: I tried the lens on my new 7D (got new at a bargain price), and it triggerred a 01 error until I thought about deactivating the vignetting correction.
Sharpness is not great at the moment, but my only tests were hand-held, so I guess this could be a good reason.