Blue Gene and its progeny will eat this alive. (Score 1)

IBM has proven with their custom Blue Gene OS that a minimal, focused and efficient operating system trumps the notorious bloat and pack-in that every modern Microsoft OS has been known for. Try and think back to the last time you've described any product in the Windows Family as "lean". IBM has also been very keen on Linux, tailoring it to Blue Gene's I/O nodes. Therein lies the beauty of custom operating systems and highly customizable operating systems, two arenas where Microsoft just can't compete. You can get what you want with as little overhead as possible.