Word has it there are many Macs in use at the Redmond campus and in Bill Gates' home. So his unfamiliarity with Windows 8 wouldn't surprise me.
When I interned at Microsoft, the building I was in had a Mac testing room with about 20 computers. It was actually a interesting room because it was all white: white floors, white walls, white tables, white walls, and white computers.
And yeah, a lot of the employees had iPhones and there were even a handful of people that took Mac laptops to meetings. Nobody really seemed to care.