me too using bsnl 675 plan which inclusive of service tax becomes 759/-
one advantage in comparison to 3g is that upload and download speed is almost same and you can do it simultaneously. upload generally at 45 kbps and download at 55-60 kbps.
its unlimited and maximum use of mine in a single month was about 25GB
but u cant use it on the move.so u have to use some data plan on phone also.i use small 2g plans just for connectivity. for downloading apps and all even on phone i use my bsnl connection, through wi-fi router.