WAIVER: I don't own this helmet, but I thought my research might help others, as I tried this on several times at various local bike shops. The look, light weight, and ventilation intrigued me and I was ready to shell the big bucks for one. I am a mountain biker who rides some suburban trails from time to time, so I was considering the Octal in one of the hi-vis colors.
First, I tried one on at a local bike shop and it felt light. Comfort was ok. Neither weight nor comfort was a real wow factor, but it was nice. The straps are like ribbons; every detail about this helmet seems very modern and lightweight.
I tried on my Radarlocks with it on, and I had the same problem that I did with my Trabec. The area of the helmet that comes down and protects the temples pushes down on the earpieces, which in turn puts pressure on my nose bridge. No go.
With my Trabec, the straight stem Radarlocks slide in between the helmet and my temples, so I tried it with the Octal. It worked, so that was an option. My Racing Jackets do the same. So the Octal was still on the table as an option.
The following week, I went to my bike shop of choice and tried on a few more lids. In doing so, the Giro Xar immediately felt super comfortable and stood out from all the rest. I tried on the Octal again there, and with the Xar as a point of comparison, noticed that the Octal felt more round than oval, and put pressure on my forehead, even with the correct size and fitting adjustments being made.
I ended up buying the XAR, which they had in the hi-vis yellow I wanted, and since it was my shop and missing its box, I got a deep discount.
My take on the Octal: I love the styling, the purported safety benefits and ventilation, and the very light weight. If it fits you, your shades work, and you have the means (and can justify it), go for it.
I wore the Xar today on a very hot So Cal day in the Santa Ana mountains, doing a 21 mile ride with 3,500' of climbing. I really dig this helmet!