I have one, and i must say it was worth the money, better throttle response, gained a few ponies, makes my auto feel more alive. I went with the CFM 67 mm throttle body.
Everyone that I have encountered who owns a Focus w/an auto tranny love them, most people with a manual say its hard to get use to, so hard they take them off and return to stock. They say you pretty much have to relearn how to drive ur stick.
So if you have an auto, ull love it. If you gotta manual you might love and hate it!