United seems to have the best mobile app among airlines.  It's cool how it takes the top part of the iOS screen to show you first) your gate, then) your seat, then) how much flight time left.  That little spot in the top of the iPhone was a cool ad in the more recent versions of iOS

Partner @USV. Student of cities and the internet. https://nickgrossman.xyz

Does it have the live push notifs like Delta for different stages of the flight (e.g. boarding, your boarding class, arrival)? 

That UX and one step/auto check-in stood out to me my last trip.