Have the Steam version, and the game just oozes potential, but as of the time of writing (9th Jan 2014), the game isn't really in a playable state.
A number of bugs and performance issues detract from the game so much, that it is essentially unplayable. I have logged about 30 minutes of game play since release, as I just haven't been able to bring myself to commit any more time than that.
I have a relatively high end PC (AMD FX-8350, 4GB GTX670, 8GB RAM, SSD, etc) and run Battlefield 4, Crysis 3, Hitman: Absolution, Tomb Raider, etc at 90+ FPS, yet average around 15 – 20 FPS in Rebirth, regardless of graphical settings.
That said the scope of this version of the X Universe is impressive, and once the bugs and performance issues have been ironed out, it will be a real keeper. On the up side, Egosoft have always been very good at supporting their games, so it is only a matter of time now. Give it another month or two…