Hi Ravi,
I can't comment on the condition of lines in the Punjab area, so speed may vary from region to region. (I'm in Bangalore)
It's true that you are getting a DL speed more than what is guaranteed (i.e. 256 kbps). However, the amount you are paying for this connection (Rs. 750) is totally not worth the speed even for an unlimited plan! (considering BSNL's other plans' speeds)
For example, you're better off going for Home 1000 with night unlimited (2 am to 8 am). This has a baseline DL speed of 384 kbps which claims that it can go up to 2 Mbps.
Here's the shocking, but good, truth - with this Home 1000 plan, I now consistently get around
2500 kbps DL and
400 kbps UL speeds!!

And it has night unlimited. (I havent posted my speedtest pics but can once i get home)
So, IMHO, the extra 250 I think would be a very worthwhile investment. Even better if you can afford the Rs. 1500 512 kbps NUL plan. Dont worry about not having a full day unlimited connection. Look on this forum for instructions on automating your torrent downloads at night if needed (I don't imagine you're downloading heavily during the day). TRUST ME, it's much more worth it...
Good luck!