Took the Airport Express from Hong Kong International Airport into the city and it was so simple, high tech and efficient, not to mention clean! There was news on flatscreen TVs, individually controlled volume built into each seat, clearly pre-recorded announcement of each stop in 3 languages, and interactive map in each car that shows where you are in the journey and lights up the destination on the map upon arrival (also widely deployed in Europe). I was very impressed with the efficiency, cleanliness, visitor-friendliness, and tech saaviness.
I plan to travel by the Hong Kong MTR subway system next within the city. Will do a quick comparison to BART when I can.
Update (2/1): On the way home, we took the Airport Express back to Hong Kong International, and as we arrived at the Airport Express station, we realized that you can actually check in for your flights and drop off your luggage there because every major airline (ours was United) had its own counter at the tram terminal. It is brilliant, not to mention simple! It eases congestion on the Airport Express trains, it frees the travelers of heavy baggage, it saves you time later at the airport check-in terminals, and as baggage-free travelers, it is easier for us to spend our money at the airport shops and resturants! Very cool! 24 minutes, luggage-free ride to the airport.