My family just completed a trip to India and we had the concierge at our first hotel in Delhi get us some SIM cards. It took him less than an hour, basically while you eat breakfast the first day. He needed some passport photos that we brought with us and a copy of our passport. We ended up with two cards on AirTel and two on Idea. We put Rs 1000 on each card and they last a little more than 2 weeks, the duration of our trip. We used them fairly frequently and traveled all around the country. The local calls in Delhi when we got there were billed at 1p/sec, Rs6.4/min to the US (about USD 15 cents/min. When we were in other parts of the country it was Rs1-1.5/min for local calls and 9.4/min for calls to the US.