Marathon: The game takes considerably longer to complete.
The Greater Good: Psionics can only be learned from interrogating a psionic alien.
Absolutely Critical: A flanking shot guarantees a critical hit.
Red Fog: Combat wounds will degrade the soldier's mission stats.
Hidden Potential: As a soldier is promoted, stats increase randomly.*.
Not Created Equally: Rookies will have random starting stats.*.
New Economy: Randomized council member funding.*.
Damage Roulette: Weapons have a wider range of damage.*.
Many of these are unlocked after you beat the game-if you've already completed XCOM, you should see the full list. The free update includes (but isn't limited to) the following options.