Iï¿½ve had an Octal for a couple of years and love it. Light and airy and you forget you have it on. The fit system is easy and works great. Bought this orange version for my son and he loves it. The bright orange color looks good and is highly visible. I can now easily spot him when mountain biking in the woods!
I first bought a giro aether and returned it after trying it on a couple times. It felt like it sat over my head and the spherical mips felt too loose, like it would slide right out of the way with a crash. Could move the thing around with my hands easily, felt gimmicky. Parts felt cheap too. Got the protone and it is a solid, perfect fit. It sits around my head and is snug yet comfortable. I have a somewhat ï¿½longer/skinnyï¿½ head. Strap and parts are much more robust and I like the leather chin deal. MIPS would be nice, but it feels great. Put in a good amount of miles, but no real tests.
Pros: Well ventilated, cutting-edge MIPS, good looks, great straps and adjustments
Cons: Difficult to fit versus prior Giros, allows sweat down the forehead.
I used the sizing chart as recommended given the different MIPS design and it said medium. Medium felt tight at the rear sides of my head -- like a flat spot pushing against the helmet. Tried large but it was HUGE on my head. I ended up with the medium -- very snug, almost too tight, but when I ride I do not notice this. I wear large in other helmets with no issues. The fit of this one is DIFFERENT, so hopefully it fits you better than me.
The front padding is from temple to temple which is nice but it is very thin. It takes very little sweating to saturate the pad and have sweat running down your forehead even with wearing a thicker skullcap such as Headsweats. This is much more of a problem with this helmet than any of my other helmets.
Summary: nice looking helmet with great tech and features, but the fit is more difficult and the front padding is not as absorbent and allows more sweat down the forehead -- perhaps a function of the tighter fit of the helmet on my head.