I really liked the movie, however, there were some plotholes that left me going 'hmm. ok?
Spoilers:-------------------------------------
The first were very precise scenes that set up questions, that werent answered.
There was a trailer that stated, not exactly this but close:
They are here now, and not for the reason you think, however, the reasons for being here were never addressed. As well as scenes that were set up as questions and the movie eluded to answers, and then just went the opposite direction. Like the reason the command module dropped.
Worse, was the fact there were so many weapons, when the aliens were 'brought down' by the military. Especially the mech suits. They sort of lost the staging to add cool. However, they really did add cool!
I didnt catch what happened to the leadership, though someone told me that a disease killed them. I must have missed that, because I remember them saying they were sick and the leadership was gone, but I didnt hear them say they died from a disease.
--------- end spoilers.
That being said, I really liked this movie. I thought it was a solid premise, based on human fear, specism etc. I though the special effects were extremely well done for a 30 million dollar film.
Favorite part? Using the gravity gun to kill a merc with a pig. Priceless.