I had been to New Delhi Airport a couple of time in my life because it is the only airport near to my hometown. I have travelled to Chennai and Bangalore also via Delhi domestic airport and it is the best airport I have ever visited. The ambience is just awesome. Accessibility is just awesome, as we can get airport line metro from New Delhi Metro station or easily we can get AC buses from ISBT and different part of city.
They do offer 45 minutes of free wifi that works great and after 45 minutes you need to pay, if you want to access more. The waiting area is just awesome, fully neat and clean and so many food outlets are there. I had my flight from Bangalore to Delhi and I reached Delhi Airpot at around 1:20 am in the night as my flight got delayed, even it eaily I got bus just from the exit gate. The facilies are just incredible.