[nkurz]

I agree it's still a somewhat open question, but I think the data is that Massachusetts is probably on the side where it can make sense with the right equipment. Here's a real world analysis of a heat pump in Connecticut that averaged an full heating season COP of about 3.0: https://www.nrel.gov/docs/fy13osti/56393.pdf

I disagree that he's unlikely to have chosen a bad installer. They seem to have installed a non-cold-climate heat pump in Massachusetts. If that's true, I think it's strong evidence that they were not competent and should not have been trusted. I guess one could argue that this was a low probability choice, but I think it's as likely there were simply no more competent installers available in his area.