I've been purchasing the I/O goggle every year since the thing came out! All I can say is...wow...just a super comfortable fit even with all sorts of helmet brands, not just smith.
Ideal in weight, snug but soft on my face, and my favorite part, being able to change lenses in about 20 seconds. Super easy interchangeability. Really enjoy the style too, you have such a great peripheral vision with the spherical lens but it doesn't give you the bug eyed look that some of the other sphericals tend to do. Haven't seen a better pair of goggles on the market, and I think smith has just about perfected it here.