I have it on my cars. Stuff is great.
Rock chips will have little to no impact. Yeah, one seemed to have gauged a little out of it on the hood, but it's protection. Car washes/waxes don't care and there's no build up on the edges.
On the head lights, it's been great for the years I have it. There has been no discoloration, fogging, or yellowing. If for anything, it should be a requirement as micro scratches, UV and road debris does take their toll.
The fog light install seemed to have had a problem though. It usually goes on with a slightly cloudy film which dries up, but the fog lights never seemed to have cleared up 100%.