End-game time for XCOM: Enemy Unknown with the Enemy Within expansion. Overall, the expansion helps flesh out the entire game and I'm glad I waited until it was out to play it. Let's review:
1. The expansion puts in new content starting atthe tutorial missions at the start of the game and the effects last throughout. The Second Wave options are all worth a look, too. You WILL wish you made a bigger push for MELD if you aren't aggressive in fetching it, though.
2. The EXALT side missions get boring and repetitive after a dozen covert ops are used to nail down their HQ, but their tactics are different and thus still make for a refreshing change even during the end of that plot thread. They're a great addition overall. These missions seem to take council mission out of focus until they're wrapped up, though.
3. Gene mods are mostly useful and priorities for each one can vary a good deal depending on class. Having a squadsight sniper scale a 3 story building instantly to get a firing position that covers half the battlefield or an assault trooper remaining invisible when a berserker walks in is priceless.
4. MEC troopers can be made broken by using a colonel-level sniper as the base since the aim stat transfers and they play like an assault/heavy soldier. From there, it's hard to go wrong with their skills unless you're min-maxing at a higher difficulty. Unfortunately, a fully upgraded one costs as much or more than a fully gene-modded soldier, so it's best to stick with 1 or 2 MECs, though multiple MEC troopers are OK to play with.
5. The new enemy types help keep things a bit fresher, but I wish there were a couple more. Those that ARE added don't disappoint, which is why a couple more would be so welcome.
6. All of these things tie in quite well with the main game to keep things balanced. I have only begun to feel overpowered now that ALL research projects are finished, weapons and armor are fully upgraded, and I have a squad full of colonel-level soldiers. Survival may be most difficult during the first month, but missions remain dangerous for your troops until the end. Well-executed tactics and base management are critical until then. It's only a shame that they peter out towards the end.
7. My Polish sniper speaks the language but still goes "hasta la vista, baby!" when plunking a mechtoid from across the map. It's FANTASTIC.
Seriously, though, this and Xenoblade have been my two favorite games in a long, long time.