I've now had my Octal for about 2 months and can say this is one of the most comfortable helmets I've ever worn. The fit is great. I was deciding between the Octal and the S-Works Prevail and found the Octal to be a little more comfortable (9.5 out of 10 vs. 9 for the Prevail. The S-Works Evade would be a 10 for me), but the straps really make a difference. The way they are tied in with the helmet makes for a very comfortable fit around the ears and I find it snugger under the chin when done up. The straps aren't insanely long like my old Giro Atmos either. The adjustment system in the back works well, though adjusting it while wearing it can be a little tight. I found that I've been able to set it and forget about it though, as compared to the Roc Loc system on the Giro that I had to adjust every time I put on/took off the lid.
The helmet shipped with a reflective "night cap" cycling cap which was a nice touch. Comfortable and certainly appreciated in the cold and wet. Climbing in the sun the other day without the cap the venting was absolutely superb/
While I'm a little disappointed we didn't get the ultra lightweight Euro version, the Octal is still very light. I noticed it a bit riding around, but I think the comfortable fit helps feel like it isn't really there. I did notice the lighter weight on the descents, ducking my head in the tuck.
I've used Oakley Jawbones/Racing Jackets and Spy Screws with the helmet so far. The Jawbones fit ok, if worn under the helmet straps. The Spy Screws will NOT fit over the straps, they must be tucked underneath. If done so, they fit fine. Both pairs work well with the eye garage.
I'm very pleased so far. If you're particular about your eyewear, try them with the helmet before you buy, but if you can get over the mushroom look, I'd definitely recommend the Octal.