For Details: New York Times
Much of this is low hanging fruit, such as using less antibiotics for sinusitis.
Other recommendations may be more controversial. In 2009 evidenced based recommendations to do less breast cancer screening were met with a firestorm of criticism. Current recommendations to do less cancer screening may meet a similar fate.
There will be another controversy, whether or not these guidelines would protect a physician using conservative treatment protocols from malpractice suits. In my experience, probably not.
Eventually payment bundling and new payment schemes may accomplish the "rationing" via a different route.