I have an old-school one that was unvented, and thus got pretty hot at about -5C and up.

Last month I had a new Giro snow lid with the open-close vents in my hand at the checkout line, but at the last minute tried it on with my googles... and found it didn't even almost fit. Seems it was designed to fit with Giro goggles. Oakleys.. notsomuch.

That tirade aside, I think it's a great solution for riding in the winter, just make sure it fits your head AND your preferred goggles.