I worked for CIGNA for nearly 30 years prior to retiring. Their Phoenix set up has been in existence for more than a decade (probably 2 decades) and is not a new situation. It appears to have worked well for those in Phoenix.
As for the United, it's interesting what they are doing. As with most things in life, there will be positives and negatives. The insurance industry is heavily regulated by each state and they will not be able to operate outside of those regulations. If there are problems reported in the 'quality' of care, the legal system can be invoked to take care of them.
I wrote in another post the other day that if I had been in an HMO, I would not have been diagnosed. That is my greatest concern when I see items such as this.
To me, this is going to be a watch and wait situation --- it will get large media attention if there are problems.