A few thoughts...

If your bank charges you a per-transaction fee, be aware that most ATMs we used in India limited us to 10,000INR per withdrawal (less than US$200). So if you need to get a large amount of money, you'll have to do multiple transactions, and the fees will add up quickly.

Also, the ATMs will most likely only issue 500INR notes, which can be difficult to use for small transactions (though we did find some that offered the option to mix 500s and 100s). One problem we encountered in India is that NOBODY likes to give change. So if you need to buy something for 100INR, and you give them a 500, they will hem and haw and ask if you have anything smaller. Only when you threaten to walk away will they finally give in and give you change (or sometimes they will have to go to another shop to get change from them). It was weird. 500INR doesn't seem like a lot of money (less than US$10), but we had difficulty passing them in many places.

If you use a money exchanger, ask for a lot of 100s, 50s, and even 20s or 10s, as it will make purchases a lot easier if you have them.