[pdevr]

Your first hand experience is evident in your answers.

Following PCP's advice (even indirect recommendations) is good - it makes sense - of course, as long as the PCP himself/herself is a good doctor :-)

The difference between rating a doctor for communication skills and rating for actual "performance" is what makes sites like Yelp not-so-useful for this task. Agree.

>Even I have a hard time judging the quality of the radiation therapy treatments decisions and parameters of my own colleagues

Probably. But your judgment (expert/peer review) will most of the time be far superior to the layman's judgment.