Finally watched this on BRD and have to say I was pleasantly surprised. It did have the same vibe and rhythm as the first one, and that is not necessarily a bad thing. It felt more like an Aliens/The Thing hybrid due to the role of the female lead. Few negatives from me: the climatic sequence was close to ruin the movie, however, they toned it down on time. Also, I think that what kills some of the enjoyment is that you know what to expect... still, lots of tension finding out who is human or not.
They also introduce a new bit of info on the ability of the alien to replicate that clears up a plot point that was ambiguous on the first one.
The alien can't copy inorganic material (tooth fillings, etc.). In the "sequel" it was left to the viewer to decide if the character "Childs" was a copy or human. Well... Childs wears an earring. Still there at the end.
I give it an 8/10. (first one being a 9.5/10)