Hmm, add an option to turn the motion blur off because it runs pretty slow here - nice concept for a game though!
Also you really really shouldn't use fixed framerates for games. Go for V-synced. It really makes the display much better quality. Also, 5x motion blur at a fixed framerate of 50FPS will end up putting 10 actual frames on the screen per second, so it looks like it's running badly because you've actually limited it to 10 FPS.