My visor was absolutely fine until for some strange reason the Pinlock lens decided to fall apart!
The difference was obvious as the lens immediately misted up and it was only with the use of regualr sprays of Bob Heath anti-fog that I could see where I was going!
I have been trying recently to find another packet of Fog City Fog Things I bought a pack of three for £7.50 a long time ago. They laminate onto the inside of your goggle lens and are superb at preventing misting. Only trouble is nobody seems to stock them any more. Pinlock have taken over Fog City and the Fog City range currently is just the one basic full face helmet visor. Clever that, buy your competitor and reduce his range to nothing.
I dont suffer from misting as long as I can keep the inside of the goggles clean and dry. But if you stop and place them the wrong way up etc etc then once they get damp on the inside they are a mare to keep from misting.
I also use an excellent water repellent spray on the outside of the goggles which works superbly - water beads off very easy (dont use Rain-X though as its too aggressive for plastics).