OK, so as evidently the only flippin' Game Informer subscriber in any forum anywhere, it falls to me to dish the data from the issue I received yesterday.
•No black blobs in Firaxis's XCOM. The guys in suits are called "Thin Men" and they can use weapons, jump large distances, and puke disgusting goo.
•No action points. The game uses a move-and-shoot (or move-and-move) dynamic. They don't want people piddling around counting individual action points. Some will call this a concession to consolitis; others will call it useful streamlining.
•Soldiers gain perk-like abilities when leveling up; some examples given are, for a sniper, Snap Shot (move-then-shoot, not normally a sniper option) or Squad Sight (shoot any enemy anyone on your squad can see -- not sure of the rationale there....).
•Environments are destructible, as we would wish.
•Soldiers can still panic, but not to the point of wiping the squad. Likewise, you'll never get plasma-bombed right out of the carrier. They want to make the game more fair, and those were specifically mentioned.
•The strategic layer is extremely robust. You still need to choose which countries to send missions to, which offers of aid (in exchange for more protection) you'll accept from which countries, which alien technologies you'll research, etc. The back-and-forth between tactical and strategic play remains at the heart of the game.
•Overwatch, duck-and-cover, etc. are all still very much present, tactically.
•You can research vehicles, which take the place of a squaddie. They don't gain XP and when they are destroyed they are lost for good, but they provide serious cover and firepower. One example given is a mobile heavy weapons platform that serves as a good overwatcher for a tactical advance.
•Sectoids and Mutons are in. Cyberdiscs and Thin Men are also mentioned. Evidently psionics are also in.
•Aliens have their own special perk-like abilities as well.
Overall it looks really fucking fantastic and I am now DAY ONE.
The article specifically cites a sniper spending their entire turn to take an aimed shot for Massive Damage. Perhaps it's more accurate to think of the game as having only two action points per turn, for Move-Shoot, or Move-Move, or Aim-Shoot, etc.
Gus, like I said, overwatch is in the game. In, in, in the game. You definitely can set up squaddies who haven't used all their actions in a turn, such that they can do overwatch and shoot the instant something comes into view.
Reloading costs an action, so it is a tactical consideration. Ducking into cover is the main positioning mechanic they mention. They also mention supppressive fire as another mechanic -- your heavy weapons guy can lay down a barrage that can paralyze pinned units (e.g. remove their actions). Grenades are in, wounding is in. Generally it doesn't sound like there are fewer tactical options, but rather that the bookkeeping is simplified.
Apologies if the article was unclear, but the deal is that sniper rifles are unusual in that they take a full turn to shoot. You can unlock a move-shoot perk for snipers at some experience level, but your basic sniper rifle takes a full turn to fire.
Ammo is abstracted. You're assumed to be carrying enough clips to reload as much as you want, but it takes a turn to do so. Suppressive fire is crazy awesome, for instance, but it burns through ammo like a mofo so you're borrowing turns down the road to kick ass now.
Body positions - AIUI you are assumed to be kneeling behind partial cover etc. They didn't go into a ton of detail here. Personally that's a level of control granularity that I'm not concerned about preserving, so long as I have other awesome shit that I can do and creative tactics to explore. Which from what I've seen will not be lacking.
So yeah, you only have one base. Building different bases has been removed, but you still buy satellite coverage (the new radar) and build hangars for interception in different countries. Your single base is like way more crazy awesome than any base from the original, though, and presents lots of opportunities for more decision-making in terms of digging deeper as well as what kind of expansion facilities you add on (see the screenshot of the "ant farm" that we put online Monday).