This game has some serious, game-breaking bugs, as well as some other bugs that will slow down your progress that need to be considered before buying this game:
The tutorial appears to crash during the cutscene directly after the first mission, so as some people have found with the original game, you're going to find yourself learning the game through trial & error or through a wiki while trying to avoid the tutorial altogether. This has been something that has been reported through VERY LARGE dump files over & over by almost everybody, something that is going to eat up a limited bandwidth very quickly & yet the problem still has not been resolved since the launch of the game.
Seems like most of the time the removal of limited items (usually crafted in Engineering or upgraded weapons using upgrades after researching Modular Weapons) doesn't work & you'll need to keep track of who you used in the last mission so you can go remove them manually after finishing a mission.
On hostile VIP missions, you have to knock out the VIP & take him to the extraction point. Be careful about carrying a dead teammate to the extraction point before the VIP, this will cause you to fail the mission even if the VIP is still alive.
Much like the original game, placement of the land marker (the one you move with) is hard to get it where you want to at times, in some cases you may move your character where you don't want them simply because you didn't have the marker where you thought you had it based on the position of the mouse.
The overhead textures (while indoors) can be a real hassle to navigate seeing as they don't disappear as they should when you are under them, furthermore they tend to get in your way when you're trying to move your characters. The trick is finding the right angle, but it can take some time to get the cursor where you want it & an angle that the upper level isn't going to obscure your view of where you're trying to move too...
There are some bad camera angles in the game, sometimes doing a battle cutscene with a barrier in front of the action. These are rare, but you'll notice them if you stick to clustered cover often...
The UI, targeting & fog of war mechanics often times don't update as they should.
Many times your action buttons won't light up when you do have the option to use them, enemy targeting markers (above the action bar) won't show or appear gray even if you can attack them, hacking point markers won't show up even if they are in sight of your specialist.
The other matter about targeting & fog of war that I've found is that sometimes you have to quicksave & reload the game to get them to update; I've even seen situations where I could fire on an enemy before I quickloaded back to a quicksave, then lost that target after quickloading.
The game can still be played (if you avoid the tutorial), but for the most part the game is a pit of bugs you have to watch out for, so saving often can help...provided you're not playing in Ironman mode...