As an iPhone user, I can say that it would be nice to be able to have boarding pass barcode, flight status, upgrade/standby lists, and seat maps all in a single interface without having to juggle pages. It would also be nice for the BP barcode to load at the ideal size for the TSA/CO bar code scanners; that's hard to do when you have to design a webpage for multiple browsers, but easier when you're working with an app. (Hell, if WN can do it...)