This is really cool. I think that the biggest weakness is the preference elicitation, but that's a super hard problem.

Also there's the fact that there is almost as much diversity within cities as between them. I live in Echo Park; I don't think of myself as living in Los Angeles. Maybe people pick a city and a part of town for totally different reasons? I don't pick a city based on the average green space, but I would prefer a neighborhood that has a big park or beach nearby. And that neighborhood problem was the big one for me when I moved to LA. I got in to grad school in LA . . . so, ok, I'm moving to LA; not a lot to think about. But what part of LA should I live in? That was really hard to figure out.