We were in India (Hyderabad, Delhi and Ajmer) this past February and had a very difficult time getting and using the sim cards. After a day of wrangling with a local cell phone store in Hyderabad we finally got Indian passport photos taken, photocopies of our passports and paid an extra INR 200 for the owner to "take care of it". The phones worked for 7 days after which we got a call from the provider telling us that they did not have our documentation. By that time we were in Ajmer and could not get the number of the store we dealt with in Hyderabad. Next time my friend who lives in India is going to get our sim cards all worked out before we even get there.

It is no longer a sure thing you will get a sim card and the situation is individual each time, so bring along your international phone just in case. We had to use ATT for the last three days we were there.