150-500mm Sigma Sony mount (1 Viewer)

I am on the verge of buying one of these lenes for my Sony A100, I was wondering if because the lens does not have the OS will it be difficult to get a sharp photo, I only want it for birds I need the extra length for country bids other than garden birds. It must be fairly good as it seems to be out of stock in many leading outlets. Does anyone have any photos with the lens with the Sony cameras? Thanks.

I thought the Sony A100 had image stabilisation built into the camera so you don't need it on a lens???