I think it was a great movie, 8/10 for me. I can see why some people wouldn't like it. The first one was small and simple but witty, it was like a small event happening where some crew of a ship was fighting with a comador of a small army. However, the third movie was just as witty, but it was much bigger and much more complicated, it felt like the whole world was gathering to fight in one big war that will end everything, as opposed to some small event. Nevertheless, it was very fun and enjoyable. Also, great for the directors to finish the movie, right where it started only with a few facts changed. Perfect position for whatever they decide to do, end the series or film the 4th one. The story ended, but there is food for thought.
As for the length, 2 hours and 40 minutes, i guess is a bit long, but personally, i'm used to that kind of movies now, after LOTR, James Bond, Spiderman etc. Besides if i'm gonna pay 10 bucks to see a movie, then i want it to last longer, instead of watching 80 minutes of some story and then feel robbed by the box office.
Anyways, looking back at the trilogy, i'm grateful to Disney for creating such a movie and then for deciding to turn it into a trilogy. It truly was enjoyable.