Summary: Definitely good antifog properties, however the coating on the glass is not particularly scratch resistant. I do not recommend wiping it with anything! In addition, it's not multicoated like the original glass eyepiece that came with my D700. This means that light sources from behind the photographer can sneak in and cause rather distracting reflections. I use it with the rubber eyecup and still find this to be a problem.
Summary: I've discovered this product (and the DK-19 RUBBER EYECUP) when I used to shoot with a Nikon F5 outside in low temperature. Fed up not breathing while shooting because of fog problems I was looking for a solution, and this product offered me THE solution for this kind of problems. I was so happy with it, that when I got the opportunity to buy a D700 with the same kind of viewfinder, I decided to order an Anti-Fog Eyepiece even before I ordered the D700.
Summary: Very good product for my D3. I use it for everyday photography. Be careful when cleaning it. I destroyed the anti-fog surface by using a standard micro-lens-cleaning-cloth. The anti-fog cover just went off. Now I have a second one always with me. It was very hard to find this item in Sweden while on vacation..
Summary: I live in Maine where the winters can be trying. The DK-17A Anti-Fog Eyepiece works great. No more fogged eyepiece due to a inadvertant exhale too close to the camera. No problems exerienced. I did buy it again as the first was knocked off the camera and lost. Would buy a third if necessary.