Short version: This game is great. Buy it, play it.
X-Com Apoc is a strange, but completely lovable creation. It's certainly an overly-ambitious game, and not all of its features were fully implemented. But it's not broken.
The cityscape is, like fans observe, a working ant-farm. Organizations raid each other, they raid you, you raid them. Aliens are a big part of the game by they are not your only enemy.
Political and military decisions directly impact on the game and on the environment. If you are at odds with certain groups, there will be consequences. Some are obvious, like not being able to buy equipments from them. Some are more subtle. If you make an enemy of the corporation that runs the public transport system, your new recruits won't be able to reach your base. How great is that?
Forget about the limitations of the (surely great) new X-Com: you can have multiple bases, and stack them with troops and vehicles. You'll need them. Each real estate to build a base have a different price tag and different spacing accommodations. As always, you'll have to choose wisely.
This games feature a very advanced version of the turn-based game mode of the classic X-Com. If you want a good turn-based experience, this game does that.
But the real gem, in my opinion, is the real time combat engine. It's simply fantastic. It's every bit as tactical as the classic turn based, but with refinements and even limited responses from the units. They will not dumbly stick around under fire, but will, while respecting their orders, move in and out of cover to fire. They will behave like actual soldiers would, panic including. You can pause at any time to issue commands, and you can also create groups.
It's a sophisticated tactical real time engine that - make no mistake - have little to do with traditional RTS games. It's a real joy to blast aliens and enemies like that. The missions are more fluid, as well. This game feature some huge maps that are a core to go through on TB but are almost a breeze on RT.
The cityscape interception combat is fully realized on this game, and you can have huge air battles between your craft and the aliens. Sometimes the local police may even help you.
Difficulty is Adjustable. It can be set to easy, and on the hardest difficulty it can give any game a run for its money.
This game is a lot of fun, and I really recommend it.