(Spencer Platt/GETTY IMAGES)

Today’s regulation does a lot to both increase the financial incentives and decreases the risks, of participating in the program. The American Medical Association likes it, as does the American Hospital Association.

But the most important endorsement so far comes from the American Medical Group Association, which represents more than 400 large provider organizations--the exact kind that the Obama administration hopes will participate in the program.

AMGA was among the most vocal critics of the administration’s first shot at an ACO rule, back in April. In a letter to the Center for Medicare and Medicaid Services, the group blasted the early rule as  “overly prescriptive, operationally burdensome, and the incentives are too difficult to achieve to make this voluntary program attractive.”

Now, they’re whistling a different tune. My colleague N.C. Aizenman spoke with George Roman, AMGA’s senior director for health policy, and found out they’re pretty happy with the new rule.

“At first blush I’m surprised at the flexibility and responsiveness that CMS has shown,” he told her. “The changes from the proposed rule to the current version seem to be significant and that’s a very good thing. ... CMS has listened to what other people said and proposed a different approach. ... They clearly heeded what people said and it’s a big step in the right direction.”

Roman says it used to be an office joke that maybe 20 or so provider groups would sign up to participate in the ACO program (HHS estimates as many as 270 will). But he and his colleagues probably won’t be joking much anymore.

“If my first blush impressions are followed through ... then some interest will be generated that was severely dampened by the onerous [original] proposed framework,” says Roman. "I’m hoping lots of ACOs form because of the potential this model has for transforming our health system for the better.”