I use MTNL and I am stuck with it. I paid for a year. Overall the connectivity is fine. Problem is with the rented equipment Even though they promptly (After 2-3 Complaints) replace the router. Quality of all their routers is not so good. I suggest buy your own router. It will cause you less trouble.
MTNL lines works like a charm and I've not faced any server side downtime, its cheapest (when I paid yearly amount)
Good things: Cheap Fast Server are working 24/7 Connection ratio 1:22 http://mumbai.mtnl.net.in/triband/htm/tariff.htm#tariff
Bad things to Consider: The repair/setup staff cannot operate anything else than XP They never listen to your complaints and never verbally co-operate (all rigid voices, sometimes I feel they are paying me to use service) They take ages to solve simplest of problems (connection took 5 days, replacing faulty router took another 5) be patient Everytime the stupidest tech-staff shows you face, he needs 50-100 rupees unofficially Tech-people are originally their phone network repairmen, but same guys do everything
Conclusion Use your owned router, dont use rented. setting up instructions are there on website. Be patient, MTNL Office is typical sarkari office Learn Basic troubleshooting If anything goes wrong, you wont have anyone turn up for at least a week