The most interesting new way to improve your soldiers is through the medals you as the commander of XCOM can award in a little ceremony. After a few missions, you'll gain access to a medal, and you can pick one of two ways the recipient's stats will improve. You can even name your medal, just like you can your soldiers, and the medal perishes along with them if they meet their demise. The added customization options for new visuals and voices really allow you to create a squad that says something about you as a person. Because of that, the short snippet of video of your customized soldier in his XCOM dress fatigues earning a medal made me feel like a proud father; making you feel attached to your team is still one of the amazing emergent features of Enemy Within. Just don't name your squad member Michael Bluth and give him the No Touching Medal like I did. It doesn't have the same effect.
Against all of these improved soldiers is a slew of new enemies. On the alien side, the Mechtoid is the obvious counterpoint to your own MECs - a massively huge machine with a single sectoid in the center. These guys gain HP from a neural link from sectoids, fire plasma weapons twice per turn and are generally not able to be put down without concentrating all fire on them as soon as you discover them. The other new enemy is a little more subtle - the seeker is an organic flying unit that generally operates invisibly. The seeker can surprise a straggler, latch onto his face and begin sucking the life out of him. Keeping a few soldiers on overwatch is good idea if there are seekers on the map, but you can usually shoot them off without harming your teammate much. Both these new aliens must be countered with slightly different tactics, and as with the plentiful new maps, the additional variety is appreciated.
But perhaps the largest change to the XCOM formula in Enemy Within is EXALT, a secret human organization that decides to take advantage of the invasion to take over the world. They will be a nuisance in your war against the aliens, draining credits from your coffers and causing panic in countries all over the world. To defeat them, you have to expose their cells and send in an agent from your team armed only with a pistol. There then follows one of two extraction missions - a king-of-the-hill styled operation in which you have to defend zones from EXALT attempts at hacking, and a more simple download and extraction. The EXALT forces, besides being impeccably dressed in kerchiefs and suspenders, use classes similar to your own team - woe to the commander who faces several EXALT heavies and has to endure missile attacks. These missions are an entertaining change of pace, but overall the kerchief-wearing maniacs just feel annoying rather than a true adversary. They don't really threaten you enough for you to care. Once you've performed at least three of the extractions, you can start guessing where the EXALT base is and assault it on your own. That mission is interesting foil to your operations - there's even a huge hologram globe just like yours in the EXALT base, but it played out rather tame. Much more resistance was expected by this dastardly organization, but that feeds into the one big failing of XCOM: Enemy Within.
All this stuff, all the jiggery-pokery of new items and upgrades is incredibly fun and satisfying to employ - up to a point. The point at which your player skill and your team's abilities have outpaced any challenge the A.I. throws at you is when XCOM fails, and that point seems to occur earlier in Enemy Within. Even the harder difficulty levels like Classic or Impossible are only challenging for so long. After you've progressed far enough, the missions become a chore and the strategic decisions feel unimportant. Why bother deciding which upgrade to research next when you're able to completely destroy every alien on the map with barely a scratch on your titan armor to show for it? You could argue the last third of the game is a victory lap of sorts, allowing you to show off your chops as the world's greatest commander as you shoot down UFO after UFO, but I'd prefer the end game offered as much challenge as the first few missions did.
Bottom Line: Enemy Within is a solid expansion to an excellent game, with options like MECs, medals and gene mods that make you want to stomp aliens all over again in exciting new ways. The first two thirds of the campaign are definitely improved, but EW doesn't solve the problem of slogging through the endgame.
Recommendation: Grab EW if you've been waiting for a turn-based strategy fix, and bask in its alien slaughter, but don't expect the wheel to be remade. That's what mods are for.
Game: XCOM Enemy within
Genre: Turn-Based Strategy
Publisher: 2K Games
Platform(s): PC, PS3, Xbox 360