I dont know about Mumbai but Tata Sky broadband ftth has come to this "magarpatta city" township in Pune along with Airtel ftth. On the township facebook page there were a few complaints about sites not opening and slow speeds but these might be in the minority and those people might be non-tech-savvy people doing some mistake with their wifi devices and other configuration.
Overall I guess it is worth for you to give it a try, maybe dont sign up for long-term to start with. Try it for a few months and if it is good then you can opt for their long term packs.
It will definitely be better than Hathway (assuming yours is not on fiber) anyways.
I have gone thru a lot of reviews lately and most of them are negative, especially on their Google page. I don't know what to do. There is not a single positive review on their Google page and the ones that are there seems to be fake. But again, these reviews depend upon the areas they live. So, I am hoping the scenario is different or better in my area.
They have offered me free trial for a month. I will certainly decide based on this.
Is 50 Mbps (~6 MBPS) connection at 849 pm (including GST) a good offer with unlimited data? Since it's fiber optic, I am hoping there are less breakdowns in connectivity unlike Hathway.