The headlights in the Infinitah looked like crap, so I went to NAPA to pick up some Plast-x (or whatever its called). They didn't carry it, but they said this product was much better. Its little foam pads that you put on your drill and buff into the light.
The box says 5 minutes, but it took more than an hour (probably about 1:15) to get these results. I'd say it got rid of about 90% of the haze, and maybe 20% of the chips/scratches. If I spent another 20 minutes on it, I might have gotten a little more, but I was pretty satisfied, so I quit.
:edit: I should also mention that I didn't follow the directions. The directions called for spraying the pad to activate the chemicals, and then buff the plastic surface. After doing this for 20 minutes or so and not making any progress (the pad would just dry out and the "stuff" would cake up), I just sprayed down the plastic directly and then buffed on a wet surface. This worked much better.
This is the stuff I used. You also need a spray bottle full of water and a drill.