After a couple days, some more observations:
Bluetooth: One of my (few) frustrations with the OP3 was with bluetooth. It would frequently fail to pair on the first try with my car, and then sometimes I'd have to re-pair it, and sound volume was on the low side. I also noticed leaving bluetooth on would really suck battery life.
So far the Axon's bluetooth has worked like a champ: pairs quickly every time, is staying paired, and sounds really good when listening in my car. No significant hit to battery life either.
Speaking of battery life, I like that their Power Manager settings screen does a good job of calling out misbehaving apps and applying settings (which you can override) like scheduled background wake-ups rather than letting them keep sucking away. It'll also let you know if they do things like 'Keep the System Awake' or 'Frequently Wake Up the System', as well as historical records of apps with high power consumption. Nice!