I'm a fan of the first Skyline. I thought it was a well made alien movie that had some mystique to it and an unique ending. Unfortunately, Beyond Skyline takes the most interesting ideas from the first part and completely obliterates them in the most profane way possible.
The first half of Beyond Skyline is pretty good. The main characters are introduced in a very clichéd manner but I don't think that will bother the audience. Once we peek inside the alien ship things start to get really interesting. This is where the film really shines. Lots of special effects, lots of cool environments and lots of "what the *beep* are those things" moments. It really builds up a nice momentum and keeps you interested. But by the time the movie is half way through, things start to take a turn for the worse. The plot starts to get lazy, the characters start to behave oddly and the whole thing starts to fall apart. It is if the screenwriter decided "*beep* it, I'm going all in on this shit" and just destroyed the carefully crafted momentum from the first part of the movie. This is done in a gradual but heavy handed manner.
By the time the movie reaches it final stages, you're not going to care for it anymore. Why? Because the mystique is gone and because the mighty aliens are now being slaughtered in melee combat by some very vulnerable humans. But nothing can rival the final 5 minutes of the movie. You thought slaughtering aliens in heavy armor with knives was over the top? You haven't seen anything yet!
All in all, the movie is quite entertaining but it could have been much better. I feel the story could have worked if the movie had more time to develop it in a natural way. In its current form it just feels rushed and quite frankly stupid. Nevertheless, I feel Beyond Skyline deserves a watch and would recommend it to sci-fi fans.