I've owned the road version of Giro's spherical MIPS helmet, the Aether for the last two years and I love it. So as soon as this version for Mountain Biking came out I really wanted it!
It's very comfortable not having any of the MIPS plastic against your scalp but still having the safety benefits of MIPS. It's also very light weight, and the fit is perfect. I have a more oval head, most helmets sit a bit high above my ears, but this one comes down perfectly, a quarter inch above my ear, and just above my eye brows. It also covers the back of my head nicely.
The vents are quite generous, I'll be happy to have that ventilation on the warm days! It's worth mentioning too that the colors are way better in person. The matte gray has a slight bit of blue to it and the lower portion is kind of marble like. Very nice looking!