I just bought one and had the chance to wear it for the first time in Moab Utah. Having worn regular open and fullface (even high end carbon models), I have to say that this is the perfect balance. It is slightly warmer than a good open face helmet (but no hotter than some crap open face helmets I've had), but the breathability is awesome. I never felt any issues breathing, even in high altitude and desert rides. A few times when I knew I had longer climbing/Xc sections, I took the cheek pads out and it was basically no different feeling that an open helmet.
And on all of the crazy technical lines, it gave me the confidence that I was protected. I thankfully did not have the chance to test its crash capabilities, but I am satisfied with the testing it has passed.
I love it and the only thing that would keep me from wearing it all the time is fear of looking like an agro enduro dork on an XC ride.