More info re iPad on MTNL 3G
A few pieces of information:
1. Balance checking for the amount of data left on a prepaid MTNL SIM using 3G is best done, I think, by putting the cut sim into another phone, such as a Nokia. Dial *400# (sending request), and you should receive 2 SMS messages back within a minute. The first SMS gives "talk" time remaining and end date, the second gives the volume in bytes remaining (and video call time remaining, for what it's worth). To receive such information in the second, of course, you will need to have topped up with a 3G Jadoo card. If you call 444 instead, you don't receive the information about data left, although you get all other information (including a mistake in the transcription of minutes to seconds on the video call time left).
2. The price per MB seems the same for Postpaid and Prepaid 3G top ups.
3. Delhi MTNL's site says that there is no extra roaming charge for getting onto related networks (BSNL or MTNL Mumbai) for postpaid, but it provides no information about prepaid. I'm guessing the answer is the same for prepaid, though. Can anyone confirm?
4. At the low end of 3G Jadoo top-ups, there is not much advantage in using a top-up card (around 1.3 MB per rupee) over the "regular" top up card rate of 10 KB per paise (which is 1 MB per rupee) which can always be used for 3G service as well. The amount of MBs per rupee changes significantly as you go up, to eventually 10 MB per rupee, and of course "infinity" at 1800 Rs.
5. Wow, does 3G draw battery power from the iPad, much more than video or graphics use! It's still a fantastic battery, but 3G drains more than I had thought, it would.