Hi mgcarley thanks for the reply. I had tried BSNL EVDO 1 year back (connecting via USB). It was pathetic. They promised upto 2 Mbps. But it rarely went beyond 200-300 kbps.
They still promise up to 2.4mbit/s - or in some adverts up to 3.1. Who do we believe? The original poster is getting ~1.5mbit/s, but he is in Kolkata, whereas you're in Kerala, and as such there could be huge differences between the network in your respective areas, so this is one of those things where we would say "YMMV" (your mileage may vary).
It may be OK in some areas and pathetic in others. The only way to say for sure is to experience it for yourself (or if a neighbour nearby you has it, check with him if it's improved).
Could they have improved? Is EVDO stable as landline broadband?
I'd say that generally speaking, no. I wouldn't personally recommend it as a primary connection or if you're a heavy user, and I personally think that it's a mistake for BSNL to have "unlimited" data on a wireless network, as it causes the experience for the users to suffer.
I may, however, be a little biased, as I'm not a huge fan of wireless in any form. I myself keep both wired and mobile connections - but I use them very differently. I realize that many people are not prepared to pay for 2 (or more) internet connections as I do, and so take one or the other - usually whichever is cheaper.