From my experience at the interview, there did seem to be a nice balance; the students said that their social lives were good, and that collaboration was a big part of the Pathways curriculum. All in all, if social life is a concern, then I wouldn't say students at Harvard are missing out.
...However, that being said, something about the atmosphere and students did seem...off? I don't know how to put it. Compared to the other "top" programs I interviewed at, they seemed a little high-strung (stressed, maybe?). Now obviously you're your own individual, and your experience in medical school is what you make of it. This was just my perspective, from one interview day, and in comparison to some other schools I've interviewed at so far. Your experience and others' may vary.