So I did a bunch of air travel last week. I thought I'd update you all with how it went.
First off, the TSA and the Watch really didn't go all that well. All of their stands had the scanner fixed to the ground, so to get the Watch to work as a boarding pass, I had to twist my arm/wrist around, or I could try and rotate the watch on my wrist so that I was wearing it under my wrist, but in twisting it I disconnected it from my body so I had to reenter my pin. Honestly, it's easier just to use the phone. Then, when going through the metal detector in the pre-check lines, I would still set things off so I would have to remove it anyway; one employee told me to remove it before I even tried to go through the metal detectors.
At the gate, things went fine since their scanners are top-down, so I didn't have to twist my wrist. But, since the target was so small for the QR code on the wrist, it still felt like it took longer than just using the phone.
On the plus side, I use the free version of App in the Air, and the watch complication is kind of neat. However, even after arriving at the airport, it didn't switch to tell me what my gate was only until 15 minutes before boarding time. That's way too late for me, and I wish I could just have it ignore telling me what the terminal is and just the gate (since knowing what Terminal to go to at an airport is really easy to figure out).
So, mixed bag on the Watch when traveling. Being able to have your destination timezone on the watch face was handy with layovers so I knew how quickly I had to get to a new gate or whatever.
Any other questions, let me know and I'll try to answer them.