I bought this Sigma 70-300 'DL Macro Super' a few years ago with my first Canon EOS camera. It was always a bit slow to focus, but I got some pretty good 6x4 prints using it. Or so I thought. Recent examination of those pictures shows some extreme distortion. It's not so sharp either. Eventually I sold it for £20 and bought a Canon 100-300 USM instead - a much better lens. But the autofocus motor in the Sigma died. It came back, and I returned the £20. It doesn't work on the Digital bodies, even in manual focus mode. So now it's just a paperweight. Got to stop those bills blowing away somehow!
See the distortion with this lens here... in case you're wondering, the pit wall and garages should be parallel!