Senior summer

Essentially, it's as good as you make it. If your in the position I was in (summer before college) if your looking for meaningful job experience it's very hard to find - especially in a local company.
It worked for me because I was interested in a language experience which I definitely managed to get at the local company but i didn't get too much useful job experience from my job.
The social scene is fun, I mean, your in one of the biggest international cities in the world - but don't go looking for an authentic Chinese experience. It's different than what you might be used to but shanghai is not representative of china as a whole.

If your looking for a meaningful experience that might set you apart from other people this is definitely a good place to start. Perhaps on one recomendation would be to consider looking for your own housing. The provided for housing is great and convenient but it's outrageously expensive (it's an extended stay hotel after all). There are options that are essentially as good for 1/4 of the cost.