I read Ted Chiang's short story first, then saw the movie recently.
The movie is excellent, and Amy Adams, as always, is superb. I have to admit, because I am dumb, I didn't get the premise/twist while reading the short story. It wasn't until I saw the movie did I get it. Maybe it's because I'm more of a visual person.
I like both action-y (Aliens) and brainy sci-fi tv/movies. Sometimes you get both, as in Battlestar Galactica, but it's rare. The Arrival is definitely the brainy type. It wasn't slow for me because I was absorbed. The pacing, the methodical unfolding of the mystery, is just right. And I really like the way the aliens' language is translated. The screenwriter did an excellent job adapting the source. Honestly, I wouldn't have thought the short story was adaptable into the movie form.
The movie, especially in the second half, does deviate from the short story. Probably because they wanted to add a bit more plot and drama for the movie.
The short story is pretty intellectual. I read that, for the story, Chiang put years of research into linguistics. He's quite a perfectionist. I know nothing about linguistics, but the details with which he discusses the subject are impressive. In fact, the linguistics discussion takes up the vast majority of the word count. I didn't get most of it, but I still enjoyed reading it. Most hard sci-fi are hard for me to get. I'm sure someone who has taken a linguistics class would have a deeper appreciation.
The only quibble I have with the premise is that I'm not sure it works logically if you think really hard about it. But maybe it does, and my comprehension is just constrained by my particular, limited perception of reality. Anyway, it's best not to think too much about it. Just go on the ride and enjoy it.
If you see the movie on Blu-ray, there is an interview with Chiang where he talks about physics and philosophy. Very smart and interesting.
For those who like brainy, trippy sci-fi movies, I recommend Coherence (2013), an obscure indie. It might be on Hulu. The story is about a dinner party and how a cosmic event affects the workings of their reality. It's very confusing but thought-provoking. One of those movies that I can't let go and still think about years later.