I lived in mumbai for three years only. However, i LEARNT Marathi unlike the millions who come there and speak only in Hindi.
The Marathis have a Vast Historical and cultural impact. They were the warriors of the past and culturally advanced since those days. I especially love their theatre plays(which i used to watch quite a bit).
However, its sad that most people who hail from North treat the local Marathis with contempt. I've even heard a Northie guy calling a local marathi guy a "Terrorist" because he used to speak in Marathi and not Hindi.
This has to stop. If you're in their state, learn to respect their culture. I'm not stationed in Mumbai any more, but i remember fondly the time i spent there and the exposure i had to their rich heritage.