I stayed in a 5* hotel (Westin Bund) and some of my Chinese co-workers warned me to not drink any water from the top in my hotel! (Because they couldn't be sure of its cleanliness!). I was also warned to not shower for too long because I mind end up getting a rash!
Getting around the city involves using the terrible cab system. None of the cabs had AC and just opened their windows, letting in huge amounts of polluted and exhaust-fume filled air, along with the cab driver usually smoking! Also (and this is somewhat expected) the cab drivers never could speak English and so we just had to show them a map/address to get where we wanted.
Central Shanghai is massively congested and overpopulated and I would never in a million years consider having a family there. In fact, our office there has lost numerous people over the years due to health fears for their children. They have ended up moving to perceived cleaner cities like Singapore and Taipei.
So for sure, Shanghai IS big and has stuff to do, but so do plenty of cities. Shanghai has major, major negatives in terms of quality of life and especially if you don't speak Chinese (because almost no one there speaks English). To even consider living there I'd have to be paid 10X and even then I'd probably only stay a year or too. I found being there oppressive and depressing.