This is bound to happen. Microsoft is an aging giant though it still has some of the best minds in the industry.
One concern I always have hiring from such old guard companies is that the people who have worked there for long, have skills too specific to the company they come from. They need some time adjusting to different technologies and development practices.
I've seen a handful of companies with employees who couldn't get the idea that practices that are appropriate for Microsoft aren't appropriate for small startups.
That said, I would take an ex-Microsoft over ex-Boeing or ex-Washington Mutual anyday.
One concern I always have hiring from such old guard companies is that the people who have worked there for long, have skills too specific to the company they come from. They need some time adjusting to different technologies and development practices.