I hadn't ridden much at all in nearly 15 years when I bought my Savage and the previous owner had installed a National Cycle windscreen.  I've kept it on and really hadn't realized just how much wind it had blocked.  I'd purchased a National Cycle Flyscreen on eBay several months back but decided to wait until spring to swap it out.  I did that last night.  The 24 mile ride to work this morning (much of it at 65+ MPH in the HOV lane) really let me know the difference.  I will definitely keep the full windscreen and swap back out around October.

The full-size windscreen keeps a lot more of the wind off of me.  The flyscreen doesn't even come close.  For that matter, I'm not sure it does very much at all but I haven't tried the bike with no screen at all to be able to tell the difference.

I removed the screen today to polish and remove any built up rust under the brackets, and it's a totally different experience riding it.  I'm spoiled with my full size shield.  Mine's mounted on the forks, so it's pretty darn sturdy.

An update ... had a chance to ride this past weekend with the Nat. Cycle Flyscreen I installed over the winter ... and have to say that it makes a some difference over riding without ... namely, in that there is a noticible reduction in pressure on the chest and arms at speeds over 60kph (40mph) ... which allows for a more relaxed grip on the bars.