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