It was bad. Not gonna lie to you, I expected more. A lot of the plot is changed, a lot is omitted, some characters from manga/anime don't appear at all, like Ervin, or Levi (though there is a guy who's supposed to be Levi, I think, only his name is different). And I think they switched Eren's and Mikasa's personalities, coz in the anime Mikasa is the grumpy one and Eren is the cheerful one, while in the movie it's the other way around. Armin seems lost as usual. I missed seeing the Armored titan here. And some scenes, like the (near) sex scene, made me so confused and uncomfortable that I cringed. The CGI is as good as it gets, the titans are shown as somewhat deformed, but still human-like.
Ended on a cliffhanger (though from manga/anime I know what happens next).
Overall, I'd rate it 3/10. That being said, I can't wait for the next part to come out. Hopefully it's a bit better.