I am still 50/50 about X4 I brought it now because I have all the others and it would be a shame not to have this one, however I am well aware that every X-game performs sketchy in the first six months as usually US the community have to go and fix everything and we get like 2-3 patches every two weeks from Egosoft and then after the major bugs are gone we get the "missing" content and features. Look at Rebirth for example on this it took almost two years to full develope into the game it should have been at launch.
What X4 appears to be is Rebirth's engine progress transitioned into a half-finished dev cycle to please X3 fans, So far I am amused in some ways annoyed in others as while flying in space I have well into the 70s FPS but I land on any station ANY AT ALL and the frame rate tanks to 25fps and adjusting the video settings to low or anything makes no difference what so ever. I sort of think it is because of my now well dated Intel i7 3820, but the AMD R9 290x I have should be able to run this just fine.
Tho yes you would think they would have just ADDED the stuff missing from X3 into Rebirth and extended the shit out of it into a new title. I am actually unsure how they managed to backtrack the IMO ONLY GOOD THING about Rebirth (gfx and stations)