After watching this film yesterday evening, I felt unsettled and wished I could watch it all over again to really appreciate it.
I could use many words to describe Arrival, but intimate sums it up pretty well, as to me this film is not only about first contact with an alien species, but also about how we perceive reality and therefore the choices we make. So, if you love films like Independence Day and the like this is not a film for you.
I won't say more because I don't want to spoil your own experience of this film... and because I found a very good review by Nate Zoebl in Rotten Tomatoes . Enjoy!