There's only a few things I've seen from previews that aren't in the game
* Factions. Well, I'm only on my second system so I can't really say for sure, but there were supposed to be procedurally generated "gangs" (different from the hand-crafted alien races) that filled the universe and fought with each other. It's possible that I just haven't hit a border where there's fighting, but I haven't see any kind of narrative bits to suggest what faction area I'm in or how to increase my standing with them.
* Planetary orbit. Planets were supposed to orbit around their star, but this seems to no longer be the case. I haven't seen any planets that are close to their stars. In general, star systems are much less of a realistic simulation than Sean led us to believe.
* Portals. Well, the structures are still there, but no one seems to know how to turn them on. My guess is that Hello just shut them off before shipping. They seemed to be working during the preview where Hello showed them, so I'm not sure what happened there.
* Giant creatures. I haven't seen anyone reporting 100-foot tall dinosaurs.
Everything else is pretty much as described in the previews.