During my visits to delhi Metro was under construction. so did not enjoy that. BTW
, once I just been on the airport for entire night to board first flight in the morning. Due to some urgent work I need to be chennai next day morning. So got into a train from chandigargh/mohali to Delhi and reached in the night. My flight was early morning. Did not want to waste money in accommodation just for 7-8 hours and more over as guralla said have to leave early from hotel need to wake-up at correct time. so simply i stayed in front of airport [i think waiting room] then took the flight and came home.
It was nice experience actually.