I have been using BSNL 3G connection since more than two years and I can assure that it is not the best so far as its availability is concerned. In order to access 3G data on BSNL mobile, the mobile network must be set to WCDMA/GSM mode. But the [problem is that it is not accessible in remote areas of a city or in rural areas. Not speaking about Internet, even the mobile service is also disconnected sometimes too. But wherever it is accessible, it provides a very good data access speed.
On the other hand, if the mobile network is set to GSM service, 3G service is totally disconnected. I would still recommend it but prior to accessing this service, one must verify if it is accessible at the residential house or not.