I am using Vodafone sim card since last 4 years, and will continue to use it because the service that they provide is really awesome. It is the largest network provider and hence the call drop is minimum as compared to other network provider .
The speed of the internet is dam good, 2g speed of vadafone is much better then 3g speed of other network provider.
Little bit costly as compared to other network provider, but then its value for your money. Overall it is recommended for all users in Mumbai.