"In the past Microsoft has always had the lever of the desktop monopoly to use in conquering adjacent markets"
That's the only sort of marketing Microsoft know. The Metro/Win8 mess is Microsoft disrupting their desktop business to serve the needs of marketing mobile,tablet and embedded devices. Instead of building new product and new marketing they simply pervert the existing monopoly so it can carry on as normal as a coercive marketing tool. It seems there's no limit to how much they'll screw over desktop users along the way.
BTW XBox had one major value to PC users: it forced game writers to use DX9. That largely defused their Vista/Win7 strategy of hooking gamers into updates by not upgrading XP beyond DX9. There are only a handful of games that won't run on XP, giving little pressure to upgrade for most gamers.