He was also the first Indian Prime Minister to be convicted of corruption, though the conviction was later overturned. In the messy, generally amoral world of Indian politics, it's not the worst of all possible crimes (indeed, I suspect Rajiv Gandhi was guilty of much worse). And the prosecution against him probably had more than a little to do with the fact that the Opposition, which came to power later, had a bit of a grudge against him.
See BBC obituary. Also see the Narasimha Rao page on Wikipedia (already updated!).
On the bright side, he held the country together. He was part of the freedom struggle in the 1940s. He translated novels from Telegu to Hindi. And he himself wrote a book called The Insider that I have long been curious to read.
History might forgive his failings, especially since he and then-Finance Minister Manmohan Singh started a process of change that has made a big difference in Indian life. Here's a little bit from Salon:
The two men [Rao and Manmohan Singh] wrought a financial revolution in a nation where Soviet-style economic policies had long held sway: slashing subsidies, launching the partial privatization of state-run companies and inviting in foreign investors. They also dismantled what was known as the "license raj," the vast, complex system of regulations that forced businesses to get government approval for nearly any decision -- often at the cost of enormous bribes.
In a 2004 interview with NDTV television, Rao said he had no choice but to launch the reforms.
"There was nothing more to do. You had no money, you were going to become a defaulter within two weeks," he said. "Once you become a defaulter your entire economy, your honor, your place in the comity of nations, everything goes haywire."