This vinyl headlight cover is a cool thing to try if you just want to give the bike a little different look. As you can see, it does radically change the front of the bike. Various makers will claim there is no light reduction, but of course that's complete crap - anything you put in front of the headlights has to decrease light transmission. If you don't believe that, you'll have to take it up with Einstein.
So sure, there will be some decrease in light brightness, but with my cover from Planetsuperbike.com, the effect was minimal - maybe a 10% reduction. Installation is easy, and it won't break the bank. You can remove it at any time with no hassles at all - so go ahead and try it when you feel like dressing the bike up a bit!
You may want to look around the web a bit, but Planetsuperbike has a very large selection, and I was really happy with the quality of their product. So go there first. Cost about $45.
This product merely attaches to the front by adhesive. It is cut to fit your lights perfectly, but you will have to stretch it to make sure it gets applied without any wrinkles. You do that by using a heat gun on the lowest setting, and absolutely make sure you start out with the heat gun more than a foot away from the cover. You'll be amazed how easily the heat gun can totally melt and ruin the material - and then you're out $45!
Start out by stickin one corner of the cover onto the headlight, then while you continue to stretch the cover out with your right hand, apply very low heat with your left hand, gradually laying the cover down, and smoothing it out while still warm. It does take some practice and skill - so go very slowly and be sure not to ruin it by burning it all the way through with the heat gun.
When you're all done, you can use an exacto knife to trim off any extra material at the edges.