Palpali Kancha: Don't worry about it. I have flown via Delhi many times. I got more hassle in Kathmandu than Delhi. In fact, there was no hassle in Delhi at all. As much as we love to hate anything about India, I was left with the impression that Delhi Airpot might be congested and small compared to the number of flights in and out of it (I think expansion is underway), there was anything but hassle during my transit there. Couple of things you should be aware of:

After the you leave the plane and get into the building, make sure you do not clear immigration as you are there only in transit. Look for Air India staff who will register you as their transit passenger. They will make sure that your luggage is retrieved by them (not you) in Delhi and will get you to inspect to ensure that everything is in order. They (not you) will then send the luggage to the Kathmandu bound flight. They will get your boarding pass and give it to an hour or so before your flight. You have nothing to worry. Just brace yourself for 12 hours in a small crowded building with one or two restaurents with really disgusting food...