I bought these goggles because I wanted the best goggles on the market, period. These offer huge visibility, great lens quality, interchangeability (which is saving me from buying 2 different goggles), and they look cool too.
However, there are some downsides to this goggle. If I'm skiing hard, they tend to fog up in the afternoon (regardless of temperature) because (presumably) they're not venting moisture. They lack frontal vents, and on dry days, I find myself airing them out on the lift. On moist days I just look through the slowly-developing peripheral haze.
With this lack of ventilation in mind, I have realized that I could buy two pairs of Phenom's for the price of the I/O's, which means that in the case of a crash, I could whip out a second set of goggles that are completely snow-free. Replacing the lens on these doesn't remove snow from the rest of the goggle. I have since Purchased the Phenom's, and the visibility is similar (though not quite as good top-bottom).
So, considering the cost and the lack of lens vents, if you have a tendency to fog up goggles like myself, I'd recommend 2 pairs of Phenom's instead. However, if you don't work that hard on the slopes, or find that your goggles never fog unless you crash (and you don't crash often), and you want to look freaking cool, then get a pair of these!
Oh, it's worth nothing that both these and the Phenom's fit my nose better than any other goggle on the market. I broke it as a child, and have had a more prominent bridge ever since. This means that most goggles/eyewear don't fit me without constricting nasal airflow. Even with a helmet pushing these down a bit, these (and the Phenom's) are the only goggles that have a wide-enough nose hole to make a comfortable, non-constricting seal over my nose. Because of this, I will heretofore always look to Smith for my goggle needs in the future. We don't all have long, skinny noses!