finally bit the bullet and grabbed one of these last week..

http://www.aerostich.com/off-and-riding/scafs-and-masks/respro-foggy-breathguard.html

It works wonderful after a few days of testing in the mountains and cold weather. Rode all day today in the mountains without opening the visor, and no fog whatsoever! Best $25 I have spent in a long time - no more playing with anti-fog sprays and wipes for me.

It takes a few tries to get it set just right for your face and helmet.. but it's worth it.

+1 on the Respro Foggy! I leave mine in the helmet all year.