My ha'peth worth... The Dart Flyscreen (
http://dspace.dial.pipex.com/sled/) is a mini masterpiece.
I bought mine six months after the buying the bike, and actually met Steve - the designer - in London when he was looking to tweak the design to fit the latest model bikes. I can't imagine a more carefully considered and designed product.
Fitting took about three minutes, it slots flawlessly into the clean lines of the bike - unlike the Ducati model which I think spoils the simplicity of the front - and it really makes a difference. I fitted mine just before setting off on a five day, 2000 mile jaunt round France, with friends on a CBR600 and an SV650, both fully faired. Suffice to say we were all astonished by just what a difference the tiny screen made. General riding is smoother without the chest wind, and at motorway speeds you can actually 'tuck in' behind the little fellow and feel almost no wind at all. Amazing.
I can't recommend it highly enough, and at the price they're a steal.
Ben