FA Off.
I'm *so* happy the Frontier added FA Off, retained it throughout, and even spent time and effort finessing it and asking for flight-model feedback about it when it was late in the day.
It's an incredibly rewarding mode of flight for me, for stuff like docking, sightseeing, etc. Having a heavy-feeling ship under control, when every twitch, breath and reaction needs to be controlled to stay on course? Brilliant.
On the flipside, when it comes to combat, I'm very grateful Frontier went with the aircraft-style of control, FA On mode. I've tried FA Off combat for the past week, religiously avoiding switching assist on, and my personal impression is that FA On combat is ten times as fun and engaging as FA Off combat. There's just something really right-feeling about it.
So... the flight system is my pick for transcendent, wonderful stuff that I'm particularly grateful to have in the game.