Brady wrote a review of Smith IOX Interchangeable Goggle on February 5, 2014
Familiarity: I've put it through the wringer
I have had these for at least 2 years now, and I generally ski 3-4 days a week. The IOXs are comfortable and stylish, and they work well for me on sunny bluebird days. Unfortunately, if it's a powder day or often if it's just moderately snowing, these goggles fog like crazy.
I don't know what it is, and I know most people don't seem to have problems, but in less than an hour of skiing, a strip of fog consistently appears at the top of the lens and then steadily works down until the entire thing is fogged. They fog so badly that water is literally dripping down the inside of the lenses. I have tried cleaning the inside and outside with a mild soap, but the problems continue. I tend to run pretty warm, and when the snow is good, I'll spend a fair amount of time on sidecountry lines that require short hikes. If I leave the goggles on, my face burns and the goggles fog. If I take them off, the moisture that has already started to accumulate freezes. Yesterday was an amazing day in Steamboat, and the IOXs were fully fogged in just over an hour of in-bounds skiing. I wear a Smith Vantage helmet which should integrate perfectly. Maybe when there's enough powder or falling snow the vents on the top of goggles clog up and don't allow air to flow, but this seems like a pretty dumb design flaw for a pair of ski goggles. I can't figure out what the issue is, but it really sucks when a pair of $175 goggles are what frequently fail me on the best days of skiing. I like Smith, but I'll have to look into other goggles from now on.
Also, being able to buy extra lenses to swap out is a great system, but it doesn't matter if the replacement lenses are always out of stock. Right now, there is only one available IOX lens on backcountry, and 8 out of the 12 possible lenses on the Smith site are out of stock. This seems to be the case whenever I look to buy a new lens.