So far the most comfortable airport to city transportation (more importantly the other way around) I found is by airport bus in both Taiwan and Korea. They have those big red soft couches you can recline and still spacious enough to raise the footrest, I sleep like a baby in those things. You have the perfect right and enough space to recline, not like on a plane with those miserable seats. BTW, check out the recently heated discussion about "Fat vs. Tall - should fat people on airplanes be treated like tall people?" on Slate.
(wow this photo was on Flickr Explore on 8th March 2010! Thanks for liking it)
It was a great trip to Seoul last week, even though 11 meetings in 2 days was a bit stretching to me. I had to move from one hotel to another due to tight budget, that happened after mid-night and I found that those SOTB taxi drivers in Seoul got to choose their customers! They prefer long distance of course. Anyway, next day's ride from city to Incheon Airport by bus was a first class ride to me on those comfy couches. I plan to spend more time on those couches than bed when I'm older, they make you fall asleep a lot quicker.