Received and installed my Cee Bailey 18" screen on Thursday evening and rode about 500 miles up to NH and then down to CT on Friday & Saturday. Yeah, I know you should always test new gear before a long trip, but it worked out well.
The wind protection is probably about as good as it's going to get on this bike. I'm 5' 7", and the major air stream hits me right at visor level. By tucking slightly, I could get completely in the quiet air pocket.
The best semi-quantitative description I can give is that there was hardly any noticeable difference over the 60-85 (actual) MPH range. With the stock and double bubble screens, I could always feel the wind starting to beat me up in the 70s and above.
Some minor downsides: The top of the screen does vibrate at highways speeds. The mounting points are secure, but the plastic flexes enough to allow wobble, and the screen is getting scratched where it contacts the "horns" sticking up at the sides of the headlight. Also, I think I noticed more sensitivity to semi truck turbulence.
One the whole, I’m about 90% satisfied with the Cee Bailey’s performance, and I think it’s a very worthwhile upgrade for longer trips and cooler weather riding.