Apparently there is a smartphone app called Ibutterfly that if you collect all 3 butterflies named "Airport" + "Express" + "Sure Thing" , you get enjoy 50% OFF a single journey.
http://www.ibutterfly.hk/eng/gallery.html
The question is, how easy is it (for a novice) to get Wifi once you land in HK?
Found some more info
http://www.tripadvisor.com/ShowTopic...Hong_Kong.html
Ok, to summarize:
-download the app.
-catch butterflies with you phone on the display
-when the first of the three relevant is yours, answer two easy questions
-catch the other two
-click on redeem --> about 3 minutes in total
-go to the AE counter with a valid Oyster card and show the butterflies
-journey must start immediately
-you cannot use it on the way from the airport, but only to the airport