Only thing that bothers me about ship movement is jerkiness. It isn't smooth and I believe it should be. About "physics" and "feel of flying tons of steel", you need to remember this is space. No forces to stop you, no inertia. Elite: Dangerous does it differently, they intentionally opted for space flight model that mimics that of airplanes in Earth atmosphere. Ships have inertia, they feels weighty, sounds affects are there to amplify that feeling.
UI is kinda horrible, especially helmet part. I'm against that shit but seems that Roberts want to go that route. UI is unfinished, many widgets missing. It will be a lot busier when done, may even be too obtrusive.
Most of the systems they are developing are lacking in that demo, probably due to instability. They didn't show air pressure simulation, they didn't show juke animations (something that should eliminate jerkiness when movement animation starts and ends), there is no grubby hands and because of that EVA looks horrible (EVA animations also largely unfinished), weapon animations are broken atm, quantum drive is obviously in very early stage. Maps are big but empty, no AI yet, no missions, nothing atm.
Game won't be finished by 2016, but maybe they'll release real Alpha before the end of this year, if we're lucky. Whole game consists of 125 star systems, that won't be done for at least another 3 years. By the end of 2016, in best case scenario we'll have some 20 systems to play in, with approx. 50 locations to visit.
I´d also get the Aurora for now, you can always upgrade later. Heck, maybe you´re lucky and there´s a short-time event where you can change your ship for another one (f.e. I was able to swap my Aurora for a sweet Mustang).
Mustang is same tier as Aurora LX (I have cheaper MR version), it is just different ship. Aurora is jack-of-all-trades good for trading. Mustang is cheap version of fighter but sucks for trading.