My scoot came with its optional windshield fitted (a father/son team were buying a scooter each but the father backed out at the last minute, they were still in the shop when I snapped it up). I barely get a breeze behind that thing and that is the way I have been riding all this time. But I took it off last month when we were getting 100′ temperatures and wow, what a difference. At speeds above 60mph I found it extremely hard on the neck muscles and the lower back. To counteract the pressure on my chest I had to either work my lower back muscles more, have a death grip on the handlebars or crouch forward. This was all distracting me from actually riding so I put the screen back on as soon as I got home.
I have heard of people who after years of riding get a full faired bike say they could never go back. My one brief attempt at going the opposite direction has convinced me a naked bike is not for me. So if you are regularly riding above 60mph in an upright position I would heartily recommend looking at windshields/fairings. Unless you just love that wind in your chest feeling 
