I have played the other 2 games in the series and this is a nice addon. The armor mechanic was a great idea, it's nice how you made different types with more health, armor and damage. However, this game wasn't without a few bugs I found.
1: The save game option didn't work for me when I did it on level 8.
2: When buying ammo, the terminal will not always give it, but it will still take your money.
3: You can buy ammo for weapons that are already at max (just needed to add that issue in incase anyone playing isn't as attentive.)
4: Just to note, the Ally A.I. is great, but I think this was the only game where he could get in the way of your shots, which can be annoying when a horde is attacking you.
All in all, decent game with some flaws, nothing that makes the game unplayable, still a nice game series, but that ending scene did disappoint me a bit after what happened throughout it.