So lets first talk about the speed which is the basic need for any broadband connection. Mtnl gives you the slowest possible speed in the amount of 1000INR, which not only is slow but also lags and sometimes pages don't even load.
1000INR is a lot of money to spend and in return you get nothing.
Secondly, the service which is the worst. The internet lags and sometimes the connection stops. So when you complain about it, all the employees of MTNL are pathrtic on their work, they gossip around in their office and are least concerned about your problems. So even if you register a complain will them it will be resolved in a matter of 2 weeks.
Last but not the least, the only thing they are best at is generating bills without giving proper service and speed. It doesn't matter if your internet wasn't working for 3 weeks, you will be charged for the whole month.
Only go for it if you want a government certified address proof and not an Internet connection.