BSNL is good dude..!! I have had no problems whatsoever with them. I'm using the BB ever since it was introduced, and so far I haven't got any overbilling probs, or connection probs..

I've been getting a steady D/L speed of around 170 - 180 KB/s since Jan 1.. Even today I D/L around 1.4 GB of stuff during the night UL time..

Maybe I'm just lucky..
Best option would be to enquire friends and neighbours in your area, see what they are using, get their opinion and then decide.. Every BB conn, be it airtel or BSNL or hathway or cablewalla, varies from area to area. Billing plans may be great in some or other, but everything comes down to how good the conn and service is IN YOUR AREA...!!