There are undoubtedly some programs where residents are mistreated so that they are unhappy due to that. I believe that to be uncommon currently in pediatrics, but would hardly claim it doesn't exist. On the other hand, "very happy" is a term that I don't think can really be applied to folks working 80 hours/week in any training program, even pediatrics. I certainly don't think one can figure it out from an interview day or from an internet discussion board. Keep in mind that some programs are, by the nature of their patient population, going to be more intense than others. Sorting out whether one likes a community vs large children's hospital or emphasis on primary care pediatrics can somewhat be done in the selection process, but even this is questionably accurate.
Bottom line is that I do not think that there is any way to meaningfully identify a good solid program where residents are pleased with the program and one where the residents are "very happy." I strongly think it is much more dependent on the individual than the program. So, do look out for evidence of a rare "bad" program, which is hard to identify, but you might get some clues, but otherwise use other characteristics to select your ROL.
