It is definitly effective at preventing your goggles from fogging up during a game. Its the best thing out there by far... better then thermal lenses. Though they don't really cool you off at all, they are excellent at keeping the airflow moving through the mask and clearing/preventing the fogging in your googles. Mine worked in 90 degree weather with high humidity.
Cheap! And I dont mean price... in fact its not really worth the price. First off it's a pain in the ass to install onto the top of your goggles without breaking it or your mask. Also, it likes to crack as mine did.
Its probably the best thing on the market to clear the fog out of your goggles. However, its hard to install, expencive, and tends to break. If you have the money and patience to install it, it definitly won't let you down. I gave this product a 7 because it works, however it can be a pain in the ass.