There are 2 styles available at the harley dealer that are hundreds cheaper than aftermarket. And yes! they help quite a bit. My fan will only come on after really hard riding. I would say that my fan runs 80% less than without the scoop!
Best 75$ Ive ever spent.. I cannot remember exactly what it cost, I got the large scoop.
100% worth it IMHO. If you don't mind spending MORE money there are much better looking setups.