Im 6'4 so getting behind a windscreen is next to impossible. I use the Givi Screen and adjust it to the lowest position - buffate free riding but still take wind on my helmet - but its smooth. With the Stock screen at any position it was buffate hell!
I have had the factory larger screen on my 04 for a while now and it's great. No buffeting, just wind noise. wind hits the top of my helmet. I'm 5'11". I run it in the lowest position which makes it more rigid. I wear a full face helmet.
I'm also happy with this screen. However, I do agree that it is rather flimsy. I also made spacers to change the rake of the windshield to match the fairing angle. Overall, for the money I'd say not bad.
I am running the optional Suzuki screen in the lowest position with no helmet buffeting. 5'9" and when sitting in my normal position, the wind seems to hit me just about at the neck line. Helmet is getting clean wind and my body is pretty much protected. At higher positions, buffeting was not bad at slow speeds but was a big problem at highway speed.