This reeks of Gabe thumbing his nose at Microsoft simply because he can, and his subordinates trumpeting the same message. Yet, has Valve done the same for Apple? iOS is just as closed as Windows RT in terms of app development, but I haven't heard Gabe rallying the troops against Cupertino? Is he still OK with Sony and the Playstation, but hating on XBox? This guy needs to learn a little about consistency and hypocrisy. A closed platform is a closed platform, a walled garden is a walled garden.
Unless Windows 8 somehow patches out its classic Desktop environment, I can't see it being omg-horribly-detrimental to gaming.