If you're a health nut, you'll want to skip this place. The food is heavy and greasy -- the signature roll is a roti with double egg, stuffed with double meat -- the equivalent of an American triple cheeseburger.
If, however you think your trek on foot across New Delhi will give you the opportunity to walk off a few calories, by all means -- give this place a try.
This and their other locations are always busy. I suspect these guys are making a mint, and deservedly so. The food is certainly not healthful, but it is delicious. In fact, my brother-in-law, who traveled with me liked the place so much that he would have eaten there for every meal if I hadn't been so keen on tasting different restaurants each time.
I was personally happy to find this place because I had tried a similar roll on the streets of Kolkata last year, and it was quite tasty, but I got sicker than a dog on anti-freeze. Nizam's gives you all of the flavor of the street, but you won't spend the day glued to the toilet as a reward for the indulgence.