I think you hit on their biggest problem now. They have (mostly) succeeded in their original goal to get a computer on every desk. What's next though? It seems to me that they need a new grand plan for the company as a whole.
But the other mission statement-y phrase that gets thrown around a lot is having an integrated experience between "three screens and the cloud". The three screens being TV (Xbox), computer, and cell phone. That gives a little direction, but as much as I'd like to see them be competitive in mobile, I'm not optimistic.
Maybe I'm cynical, but I feel like a long-term mission statement shouldn't be changing every 12 months.
New machines, granted. But that, unfortunately, is de rigueur in this industry.