Space stations are built of dozens of production and storage components which are assembled into massive space cities, replacing the haphazard "spaghetti stations" complexes of the previous games.
Capital ship combat is more epic, with each capital ship having dozens of independent shield generators, engines, turrets, and hangars.
Sectors have been replaced by proper star systems, which have points-of-interest connected via highways and super-highways that accelerate ships to truly insane velocities.
Modding is easier, as the game uses a more powerful XML based scripting language rather than the old in-game Script Editor from the previous games, and gives modders more control over the game, including the physics engine.
X Rebirth contains examples of the following tropes:
After the End/Darkest Hour/Downer Beginning: The Portal Network has been shut down following the Argons' disastrous attempt at creating AGI ships, the Community has fallen apart and everyone is at each other's throats over resources, and the Xenon and Kha'ak are stronger than ever before...
Artificial Brilliance: Unlike the previous games' questionable autopilot, Rebirth has much more advanced pathfinding techniques, to make ships fly more naturally and competently. Because the AI now looks ahead on its path (rather than only checking what is directly in front of them in every frame), ships no longer spaz out when they approach an asteroid, station, or large ship, and will instead smoothly fly around them.
Artificial Stupidity: Enemy carriers are completely helpless if the player parks his ship inside their long, easily accessible hangar. Said carriers often launch their drones from the very back of the hangar, which can cause issues if the carrier turns as it launches the drones, causing them to bounce around hilariously inside the hangar.
Ask a Stupid Question...: Meta-example. Somebody on the forum's release date thread (a.k.a. the endless-complaining-about-lack-of-information thread) jokingly asks Egosoft to come in and confirm they're not dead. Cue a dozen or so devs coming onto the boards and posting "I'm still alive." Gave the community something else to talk about for a while, at least...
Attack Drone: The Albion Skunk has these in lieu of fighters.
Casual Interstellar Travel: Even more so than previous games: space around the space cities are crowded with hundreds or thousands of individual civilian ships that fly between the stations and modules on said stations.
Diegetic Interface: The Skunk has a full cockpit with information shown on screens instead of a HUD - the game uses very few traditional menus, with almost everything done by looking at displays on the ship or by simply talking to people. Trading, for example, is done via a sliding screen that divides the pilot's seat from the copilot's seat.
Drone Deployer: The Skunk carries a wide assortment of drones - Players can directly control 4 types of drones, with support and utility drones being autonomous.
Beholder: Used for scanning objects thoroughly, or just exploring nooks and crannies inside ships and stations.
Assassin: A weak, but extremely agile drone equipped with a pulse laser.
Trojan: Used to hack ships and stations, disabling defenses or making a station vent its storage compartments into space.
Traitor: Can launch remotely-detonated satchel charges to cripple capital ships and stations.
Early Game Hell: The developers actively tried to avoid this after it plagued their previous games. The campaign gives you a freighter capital ship right off the bat and enough credits to hire a small crew, while doing some simple missions for the Heart Of Albion gives you some new equipment. You even get a destroyer (albeit heavily beat-up) a few hours into the plot!
From Bad to Worse: Egosoft attempted to make the interface easier to use over X3's. The newer interface is slower, more restricted, and most critically, has no hotkeys.
Hyperspace Lanes: Rebirth has "highways", which function similar to the trade lanes in Freelancer, allowing you to get between close locations in a system, while super-highways are used to get between different planets or points of interest in the solar system. Jumpgates are used to navigate between solar systems.
Obvious Beta: As usual with an Egosoft game. The game launched with some major performance issues, and a wide variety of glitches, such as Teladi eyes rotating 90 degrees and popping out of their sockets when talking◊. Several features necessary for empire building - especially more ship commands and a report system - are totally absent, though modders have fixed some of this, and Egosoft have stated that they'll be bringing in old features that didn't make it into the release once they've solved performance issues and bugs.
Old Soldier: Most of the Heart of Albion members are former Argon Military captains.
One Nation Under Copyright: After the gate network shutdown, Plutarch staged a coup against the isolated Argon military stranded in the Albion system, then set themselves up as the government.
Point Defenseless: Averted for most capital ships, which have dozens of small turrets to spew lasers at enemies. However, only the Arawn actually has internal point defenses for dealing with enemies which get inside the hangar.
Player Mooks: Rebirth takes it to another level compared to its predecessors, allowing you to actually interact with them beyond the command console.
Portal Network: The Ancients shut it down after X3: Albion Prelude to stop the Xenon. Part of the plot involves getting it working again. In-system travel is done via highways, a system of "tunnels" that accelerate ships to truly astonishing speeds, which have the advantage of allowing ships to enter and exit at any point.
Ramming Always Works: Averted. Automatic collision avoidance (fires the strafing thrusters to keep you safe from smashing into walls and other ships) is enabled by default, and ramming itself deals far less damage than in previous games.
Real Soon Now: For most of the game's development, there was no solid release date - originally Q4 2011, then mid-2012, and then finally a release date of November 15, 2013. Egosoft actually own the domain soon.tm.
Regenerating Health: Engineers can slowly repair the damage on the Skunk. On capital ships, they cannot repair the hull, but instead can repair damaged subsystems.
Scavenger World: The Lost Colony◊ has a Split Python from X3: Reunion gutted out for supplies, with power lines leading from the ship to a nearby installation. The Republic of Cantera relies on decades-old Terran equipment, and the majority of their spacestations are simply individual sections from destroyed Terran stations which have been patched up and used as housing and production facilities.
Scenery Porn: Egosoft loves this trope; it grows with each installment. X3: Terran Conflict was greater than its predecessor and Rebirth tops X3: Terran Conflict. Stations and ships are beautifully detailed and can now cast shadows and light sources on themselves and each other. Capital ships now use dozens of little transports to ferry cargo between themselves and stations, and each transporter has visible cargo when loaded up with goods.
Space Is an Ocean: The long range scanner borrows heavily from the depiction of submarines and boats, emitting a manually triggered "ping" that travels in surrounding space to highlight objects not visible to the short range scanners.
Standard Sci-Fi History: The X-Universe went through the Cycle of Empire twice. Rebirth is set in the Interregnum of the second cycle.
Subsystem Damage: Capital ships and space stations feature destroyable subsystems along the lines of Tachyon: The Fringe. Turrets, jumpdrives, and the ship's engines are primary targets
Super Prototype: The Skunk is a one-off ship designed by the famous Bala Gi during the Second Terraformer War, to fight against the Earth State. It's extremely adaptable, and carries far more firepower than a typical ship of its size. Excessive production costs kept it from entering production, much like the Hyperion of X3: Reunion.
Time Skip: Takes place several decades after the abrupt end of the Second Terraformer War, which was ended by the Ancients shutting down the gate system and causing the collapse of the Community of Planets.