I started using MTNL Dial up around eight months ago. Initially people (including I) were skeptical about the speed of the connection. But, all these doubts were put to rest once I started using it.
The speed of the connection is reasonably good and with MTNL’s recent decree about halving the billing rate, it is the best ISP by a margin.
The advantage of using MTNL Dial up over other ISPs is its simplicity; ISPs like Roltanet, Sify etc provide the required software in a CD-ROM that needs installing and from friends and neighbours I have heard it is not always a smooth process. In the case of MTNL, no software is required except a web browser and the phone number to be dialed.
Another plus of MTNL Dial up is it is value for money for the speed one gets and the reliability of the service. Having said this, it has a few limitations; there could be abrupt disconnections while one is surfing. One may not get connected the very first time one dials; it could take a couple of minutes to 8 minutes to get connected.