I just completed both of mine with the 3M Headlight Restoration Kit ($19 at WalMart). One great thing about the 3M kit is the instructions. Any noob could follow them and get decent results. (I did!)

I think it did a fantastic job. After I was done, I did notice that Hellfire was talking about: some scratches/swirls still in the lens. I even had one spot that was still a little cloudy. So I just went back over it with the polishing compound and the foam buffing wheel and cleared them up. (The small cloudy spot is still there, but I'm starting to think it is on the inside.)