As other reviewers have suggested, go to www.hard-light.net to get FSO graphic/sound improvements and to have access to more than twenty additional user-made campaigns, and also to other spin-offs like the Babylon 5 and Battlestar Galactica universes. User-made campaigns can be found at www.hard-light.net/wiki/index.php/Main_Page and are set in eras that span the first and second Great Wars, and beyond. I highly recommend getting Freespace 1 as well to complete the experience.
And what an experience!
Your ship controls can be customized, and are broken down to Ship, Weapons, Targeting, Shield, and Squad Command controls. Missions seem to be based on a combination of simple objectives such as Destroy / Defend / Recon or Stealth but these objectives create an atmosphere of variety and plot twists. One of the high-points of the game is the ability to destroy Capital Ship subsystems and turrets along with the extreme ship to ship dog-fighting. Another great feature is the ability on most missions to customize your and squad-mate ship and weapons loadout. This game is also missile-intensive, which creates an atmosphere of large explosions, and you constantly find yourself spinning, using afterburners and launching countermeasures to dodge the enemy. The ability to create a player that earns stats, badges and promotions gives the game an epic feel from campaign to campaign, that you will have fought in every major battle.
As a whole, Freespace 2 and the FSO universe is a must for space-sim combat fans.