I hate paper, so don’t love paper boarding passes – whether printing them at home or queuing up at the airport. Since I mostly fly American Airlines domestically I use their mobile app. One catch though is that I always pull up my boarding passes when I check in for a flight, even my connecting pass, in case I don’t have great connectivity (or there’s some other glitch) when I go to board my flight. The app saves the boarding pass so I can use it even if I can’t update it.
I don’t usually download apps for carriers I fly less frequently though, so I’m stuck with paper since I don’t want to clutter my phone. It’s never occurred to me to inject an NFC chip into my hand…