I have ridden sans windscreen, with the stock windscreen, and with the Zero Gravity Sport Touring windscreen (higher and swept up)
Picture with Sport Touring screen
[img width=600 height=472]http://i19.photobucket.com/albums/b168/mangeldbug/Blue%20Shoes/DucBlue_1.jpg[/img]
I really liked the ST screen. It does block a lot more windblast than the stock screen. When my bike fell over and trashed the screen last month though (stupid guardrail >

), I decided to just get the ZG Stock Replacement screen. Its not really windy out here, so I didnt feel it was worth the extra cost for another ST screen. With the ST screen, the wind doesnt completely miss you. For me, it hit me at my neck (I am 5'1".) With the SR screen, the wind hits me at chest level.
Screen vs. no screen is a HUGE difference. I rode around for a few weeks with nothing after my ST screen got destroyed, and although I liked how the bike looked without it, it was d**n WINDY at speed! It really took some getting used to.