"SMG is not really fast for anyone, except maybe that guy with his crazy 4.0ghz overclocked I7. More work is needed to get it to run smoothly on the machines of mere mortals...."
You can trade smoother (but slower) gameplay for faster (but no so smooth) gameplay by setting Frameskip to 1, it's the only thing that really works for me in this game and it's not that bad.