just thought I'd revisit this topic, with a news article from today's WSJ:
"Case of the Vanishing Airport Lines -- Alaska Air Speeds Up Flow Of Passengers by Jettisoning Traditional Ticket Counters"
link here (will probably expire in a few days):
link here to the article
I doubt it would work as well with UA for example, because people have far more complicated itineraries than on Alaska. But just an interesting story for the design and new approach to checkin.