I'm a little surprised be people giving low ratings to the game and explaining that it's only a slight improvement over the original Xenonauts. I mean, if you take an amazing game and make slight improvements, that should make it an even better game, shouldn't it? It's hard to make a game much better than something that is already quite good.
The game is basically a modern take on the original 1994 X-Com UFO Defense, taking the solid gameplay and providing it with modern graphics and UI, and other improvements, as opposed to the Firaxis XCOM which changed the gameplay significantly, making it more linear and simplifying the strategy layer that was so crucial in the original game. So, Xenonauts has more meaningful decisions where you can take many different paths. The difference is most noticeable on the geoscape, with multiple bases etc., although in tactical combat you also see differences (time units vs action points, the reaction shot mechanics, soldiers develop attributes rather than leveling up).
Anyway, I'm giving a 4 star review because, as a Linux user, I have to use workarounds to run the game, and loading times are SLOW, and I've had the game crash from time to time. Since the game is in development, it's to be expected. Not to mention Linux isn't supported ;) So I shouldn't judge a game harshly when it fails to do something that the devs never promised it would do. I will give 5 stars if/when the game runs flawlessly on Linux (whether natively or not, I don't mind either option).