Third, a class system has been implemented. While leveling up your troops was a feature of the first X-COM, it's been significantly expanded upon by Firaxis. Upon gaining the first promotion (level), a soldier is randomly assigned one class - Assault, Heavy, Support or Sniper - each with specific weapons and abilities. There are limited skill trees available for every promotion a soldier gains, and their benefits range from the more passive to game-changing activated abilities. For example, a Heavy can learn to lay down suppressing fire with his/her machine gun, conferring accuracy bonuses to friendly troops who fire on the same target. Many of these skills complement one another, as well, which makes their selection crucial not just for the individual soldier, but for the entire squad. While you have fewer troops overall than in the first game (you start with four and can upgrade that to six total), individually units are more valuable and meaningful than the veterans and meat shield rookies in the original game. The class system overall works excellently, and makes it all the more painful when your soldiers are blown up, melted or ripped apart in battle.
Nitpicks & Issues
XCOM certainly isn't the red-headed stepchild of the X-COM franchise, then - on the contrary, it's very good, well-balanced and compelling whether you are playing on the easier difficulty, or impossible with ironman mode turned on. The unfortunate truth, though, is that it's also underwhelming next to the original game. Features have been removed, or streamlined, and there just is not the same amount of depth or replayability to be had as the original. While the game is undoubtedly a success at what it attempts, it feels simplistic next to the dozens of other hardcore strategy titles available on PC, including the original game.
It's the little details that are gone that you really notice. For instance, alien attacks are no longer determined by UFO interception. In the original game, if you missed shooting down a UFO, it would cause a mission to begin as a result; in the new XCOM, missions simply happen no matter what you do, and are unconnected to interceptions (unless you shoot a UFO down successfully). It's a subtle difference on paper, but very significant in practice as it means you have less influence on the events taking place in the game than before. There are also no more base defense missions, so one of the coolest features of the original 1994 title - fighting off enemies in a level layout determined by how you arranged your own headquarters - no longer exists in the 2012 remake, which significantly reduces the considerations you need to make in building your base. Neither can you build multiple bases anymore - you just have one, and instead you deploy satellites, interceptors or troops anywhere in the world from a central location, which simplifies the strategy side of the game in yet another way.
Additionally, inventory management for your troops has been reduced - instead of a set amount of backpack space, now soldiers have a preset number of slots, meaning you can't micro-manage them nearly as much, or make the same sorts of trade-offs (like giving up a primary weapon for more grenades), something that new players won't mind but older players will. Enemies always receive a free move when you spot them, making it impossible to perform surprise attacks, and also removing the classic X-COM moment of coming back from an enemy turn and finding half your squad wiped out by unseen attackers. Ammo management is no longer a concern, as you can reload as much as you want and never run out of bullets. As fun as the remake is, and even in spite of the improvements, it's simply not on par with the original X-COM when judged as a strategy title.
Last, I hate to say it, but XCOM is rather unpolished. I encountered numerous glitches almost every single time I started the game up. Some, like soldiers firing their guns the wrong way, are cosmetic, but others, like very picky line of sight calculations, have a more significant effect on gameplay, and you will likely lose at least one or two soldiers over these problems. The Steam Cloud save system that is supposed to upload save files to the Internet for later use also simply does not work, judging by other comments I've seen from players. Even more serious bugs I encountered were pretty much game-breaking - one time, the game got permanently stuck while processing an enemy's turn, and another, I ended up in a menu where all the options were greyed out; in both cases I had to shut the game down using Task Manager. Firaxis have a track record of putting out buggy games, and XCOM really feels like it could have used another few months in quality control.