I loved the city personally, had a great time there last year.
One of the highlights for me was visiting Dharavi (one of the biggest slums in Asia, if not the biggest). We met some of the most friendly people there on our whole trip. If you get a chance you should visit it.
We went with a local guy called Mohammed. He was born and bred in Dharavi, has taught himself English and set up his tour business. It was inspiring to meet him and if you are going to visit consider having him show you round. You get to see all the industry within Dharavi and he give you some great insights to the city.
https://www.facebook.com/pages/Mohammeds-Dharavi-Slum-Tours/213260498684608?ref=ts
Cheers
Ben