This was an OK follow-up but not as good as the original "Skyline" in my very humble opinion. While the basis of the story was the same, the perspective was completely different. Many questions from the original movie were answered providing some closure.
There was no continuity from the first movie as far as the actors or main characters. Though there is some character overlap, the emphasis is on the new characters. One might think that means you could watch and completely understand this movie on it's own without having watched the original "Skyline". However, that would only be possible if you otherwise knew the ending of the first movie without watching it.
The good news is that if you did watch the original "Skyline", unanswered questions left hanging at the end of the movie are answered. Particularly who/what is driving the aliens, how does some of their technology work, and what happened to some of the key characters after the end of the first movie.
Overall I did think it was worth watching since I saw and like the first movie. The new perspective on the original story was good but I felt it fell short in it's execution. In particular I thought the finale at the end was a bit overdone as the hand-to-hand combat scenes seemed over-the-top to me.