On previous (shorter) visits to India, I've followed the standard advice pretty religiously -- only drink boiled or bottled water, stick to the more expensive (assumed to be cleaner) restaurants, avoid food which is uncooked, etc. But lately I've been experimenting with more of the roadside vendors and occasionally even (gasp!) drinking tap water.
One of my new favorites is fresh roasted corn. I found a reliable source just down the street. 7 rupees (about 15 cents) buys a corn cob which is roasted on hot coals right in front of you and then rubbed with fresh lime, salt, and chili powder.

The corn is cooked at such high heat that I'm sure it is perfectly safe. The fresh juices and some of the other snacks are probably a little less hygienic, but I can't resist. To be honest, for my own peace of mind, I do occasionally look away while my food is being prepared, but the taste is definitely worth it...