The authors of this JAMA Viewpoint article say the model has been a success, but the arguments are unconvincing. Here are some caveats:
The experiment is in its infancy.
Overall the results are mixed.
Cost savings have been modest and in some cases are diminishing and may prove to be transient. That's what we saw in the managed care experiment of a couple of decades ago.
Statements about quality improvement are suspect because real quality cannot be measured. Outcome data are very soft.