Buy/Sell prices - Bases are now capable of selling and purchasing items at different prices. POBs also have this implemented, with /shop commands letting you take full advantage of this. Do note that this feature is only fully supported in multiplayer. In singleplayer the 'sell' price is purely visual.
Blindfire toggle - You can now toggle your crosshair snapping onto reticles. Mostly useful for caps 'blindfiring' their guns. The desync associated with blindfiring has also been *severely* reduced. Fire away, but aim first!
Friendly Fire prevention - Grouped player ships no longer produce a reticle that your crosshair can snap onto.

- Show their affiliation on mouseover.
- Produce a natural undock animation.
- Will shoot and be shot by enemy NPCs
- If neutral, they will turn hostile if an allied NPC is hostile to the player.
- POB hostility mentioned above will only extend to the 'main body' of the base, the defense platforms continue to only ever turn hostile during vulnerability period.
- POBs Infocards, accessible by F9 keybind or the Info button in top right corner, now lists the base affiliation, base description set by the administrators, vulnerability window as well as stock and prices of administrator-selected commodities. Marketing!

- Station/Planet infocards no longer produce incredibly dull and long list of sold equipment
- Equipment infocards heavily reworked to include a very wide variety of stats such as efficiency, dps, ammo limits and so on; As well as fixing problems with incorrect data being presented, such as lack of information about multiple gun barrels, shield damage being misinterpreted, and so on.

- Selected ammo based weapons will now allow you to stock more ammo. Ammo stacking is telegraphed through the equipment stats.
Pre-5.0 also had this feature but available exclusively through autobuy, as well as not communicating which weapons could benefit. 5.0 culled it completely due to lack of transparency.

- Both Mines and Missiles can now have Arming Time property. Arming Time causes the munition to simply vanish if it collides with a valid target before a specific time elapses.
- Self-detonating mines: Selected mines are now self-detonating at the end of their lifetime.

- All systems now have an invisible wall at 200k away from the system center. Coming in contact with the wall disables your engines and stops you completely.

- Game will now render location of all group members on the minimap, instead of a single one.

- While flying through a multi-system waypoint path, passing through coordinates of a waypoint in a different system will no longer clear that waypoint.

- Not used in 5.1, but engine kill now affects all engines, instead of just the first one found. Might allow for multi-engine balance decisions in the future.