More soldier classes, more enemies, more missions and even more ways to take out the alien scum. Enemy Within, the quasi-expansion/standalone doesn't really change much - it just gives fans more.
When it comes to last year's amazingly deep strategy reboot of XCOM, 2K and developer Firaxis seem to have a 'if it's not broke, don't fix it' mindset.
They may not have fixed some of the nagging problems from the original, but those pale in comparison to how awesomely rewarding it still feels to complete a mission with your best soldiers still alive. The threat of perma-death will haunt your every move, but the reward is like none other in gaming. Take one of the best strategy games in years, add new enemies, new modes and some cool new tweaks and what do you get? A game that's somehow better than it's predecessor without changing much at all. Small tweaks to the game's visuals and audio suite make Enemy Within the standard bearer for modern strategy games. Not much has changed from last year's Enemy Unknown, but that's not a huge problem since the original was such a stellar effort.