I think I am like Big Sky on this. I rode without a wind screen for a long time. But then when I got to the Rocket III Touring, I really liked that quiet pocket that exists behind the tall screen.
Even more important than the wind and rain, at least in my neck of the woods, is that the screen really helps protect you from bugs. Bugs can ruin a ride down here in the muggy southlands.
So ... I find myself using the tall screen on the R3T. And I find myself putting the screen on the FJR all the way up. And I've ordered the touring screen for the FJR, which Yamaha says is tall enough to hide behind for someone of my seated height.
Nevertheless, YMMV. I have a friend in Maine who has two screens for his ST1100. The ST1100 is crippled in that the wind screen is fixed with no provision to change the height. So he cut one of the stock screens down to make a short screen. And in cold weather he rides with the tall (normal screen) and in warm weather he rides with the one he cut down.
I still go for rides on bikes that are wind screen free, but I do not enjoy them once the speed gets above 60 mph. Wind noise, wind force, and lack of protection from flying objects kill the deal for me.
Triumph makes what they call "fly screens" for various models, including maybe the Rocket III Roadster ... but these look cartoonish to me, in spite of my love affair with the Rocket III Tourings.
FWIW, to my eye, a screenless ST type of bike, like the FJR, looks broken without a screen.