Hi.
All things said and done personally we have found the VSNL dial up to be the best of the existing ISPs in Mumbai.
a) Dial Up connectivity with VSNL will give you an avg of about 5 KB / sec. which is not really so bad if you consider earlier you couldnt even dial in!
b) Private ISPs like Now, Satyam, Rolta, Pacific Internet, Mantra are all ok.. They are dicey in the sense that when they do well they do really well but they are down too often to be trusted. Somehow I always find them down when I have urgent work.
c) Hathway --- is a really good bet! I dont personally have I coz its not in our area yet but have heard from friends and family that the speed is awesome. The installation charge are somewhat high (approx. 15, 000) but the per month subscription is only about 1200/- which sure beats the heck out of paying phone bills.
d) several other cable options are available but they’re not so great. im using one and its so so. Downtime is about twice every week for a few hrs.
e) VSNL ISDN line is really great. You should get an ISDN phone line and use ur regular connection. A bit more expensive bu the speed is really god (approx. 20Kb / sec) and v v consistent even on the worst days!
Hope this helps :o)
Pooja.