I only had stopovers so far... (as much as I can remember because when I was little everything seemed to last sooooooooo long). My longest stopover was 5.5 hours in Singapore and then the plane was late for 2 hours due to storm.
I was so tired and wanted to go back home in Australia... Travelling France -> Australia is so jet-lagging. France -> USA is easier
One of the easiest airports for me is Frankfurt (Germany) - maybe also because it is one I practically know by heart
Jamie