I also like that people are looking at different metrics. There's just no way of knowing what to make of one group reporting an average happiness of 7.2 vs another reporting 5.8.

Are their expectations the same? Do they think about the different points on the scale the same way?

With a dif-in-dif, you could take care of some of that, but direct comparisons don't really tell you much. And, even then you don't know if you should think happiness changed or the scale changed.