I have slept in many airports, sometimes by default, sometimes planned. When I went to HNL for 3 days, I would list for a flight at night and checkin so I could get through security, then sleep in the Japanese garden. I spent 3 days in HNL for $50 and most of that was food. My last night, when I actually got stuck, I spent $10 to sleep in a grass hut on the beach on the north shore.

I've slept in ATL (many times, only once by choice), AGS (when my credit card was missing so I couldn't do a rental car and it was so late at night, I couldn't get anyone to pick me up), I got my best sleep ever in ATH (I never even realized 2 other people came to sleep beside me, SEA twice, AUH (as a confirmed pax with a long layover), SLC more times than I can count, HNL (once when I was stuck, on the next trip, 2 times to save on hotel costs), DTW, MSP. I know I'm forgetting some, these are just what I can think of off the top of my head. I am more of a budget traveler than a comfort one. I can sleep anywhere, I've always been that way, might as well save some money. I also pack light (I can use one backpack for a weeklong trip) so I use my backpack as a pillow, put myself in a corner where access is limited and hide anything important on my person.

Interestingly enough, I'm going to SIN next week, in part just to visit the airport since I've heard so much about it. I am getting a hotel room there though for the night and I'll do a quick tour of the city, not just visit the airport.