I am from pune, and I got my Dataone connection about a couple of months back. Let me speak about the following :
Pros :
1) Speed : I have the 500 rs plan which gives a 256kbps connection. I was pleasantly surprised to see that the minimum speed that I get is 256 and it tends to go upto 400-500 kbps at times.
2) Reliability : The total downtime I have had with BSNL in the past 2 months has been about 5 minutes. It is simply amazing and totally reliable.
3) Price : Definetely the killing factor. For 500 its totally worth it.
Cons
1) Technical Support : I have heard from others that its not the best. Frankly I havent had the need to use them yet
2)Confusion : There is a lot of confusion as to whether it is going to remain unlimited or not. Whether those applied after 31st March get unlimited connections or not. I think BSNL has not done a great job in communicating these queries.
Overall , by far the best service provider in India right now