I would argue that by other measures, Microsoft under Ballmer has not seen improvement either. These might include market power (the power to dictate future market directions), product sales share, product mind share, cultural association, recruiting, innovation, etc.
That said, I think there are a few areas where Microsoft has seen improvement under Ballmer. Xbox went from a "what? really?" product, to the clear console leader. And Microsoft government affairs is miles ahead of where it was under Bill Gates--from its own federal conviction, to instigating multiple actions against competitors.