I've been seeing a lot of people talking about throwing pnp HIDs (and LEDs too) into their headlights and foglights, and thought I'd share this article. While projectors aren't bad for glare usually, reflectors are an entirely different story. Daniel Stern does a good job of explaining the physics responsible for the problems, glare being the worst of them. There's also a video in there too.

Daniel Stern Lighting Consultancy and Supply