If you are talking about the Vstream, I have the same question. I knwo that most people are saying that the stock shield on the 06 is fine but I have a bunch of wind noise right at my ear level in my helmet. Looks like this might be the ticket but I would like to here from someone that has bought one first.
I have been using one for the past 2 weeks. It works very well. I have an 03 and have the stock windshield and the tall Yamaha windshield as well. The v stream has much better protection, is quieter and less buffeting around the helmet. In addition it is made of Lexan and therefore is much tougher than plexiglass and would give better protection from rocks, birds etc.