I've installed 3M, ClearShield and now a newish one, Suntek, on vehicle headlights, and I can tell you right now, they are worth every penny if you either run your vehicle through car washes regularly, do a lot of interstate travel, or live in areas that lay cinder or gravel during winter.
3M is okay, as is the ClearShield brand, but I've noticed that they are not as optically clear as the new Suntek version.
I'm running Suntek on a few vehicles, including my 4runner and wife's van, and they show zero reflection when the lights are on, something that I didn't care for with the 3M material as it reduces your light output by a good amount.
So far, the material's been on my vehicles (and a couple customers vehicles) for about 4 or 5 months now, and with my wife running her van through the car wash weekly, there's zero sign of any scratching, hazing or cloudiness.
My suggestion is to find a paint protection shop that uses SunTek films, head over and take a peek at the material. You'll immediately notice a difference in clarity against some of the other brands. You can also see what they'll charge you to do the headlights and/or foglights, as the 4 runner's lights (at least the earlier version, like my '11 SR5's) are not easy to wrap and will require at least 2 pieces to do it right.