TLDR: Well, it's better than the first film...just don't think too hard about it.
Full review (minor spoilers ahead): It's an overly long second film which plays out as a poorly executed sci-fi rip-off of The Magnificent Seven (which of course was a Western rip-off of the classic Akira Kurosawa film Seven Samurai), with more explosions and less interesting characters. The extra backstories tossed in there only add more time to the film without adding any real value.
Most of the characters remain flat and while there are good actors, it doesn't make up for the so-so writing, dialogue, and unnecessary exposition. The most interesting character is the robot, mostly because he remains somewhat mysterious.
All in all, the action sequences are pretty good, but we probably didn't need a slow motion hero shot in every.single.battle.sequence. Not to mention the slow-motion farming scenes.
Speaking of that, why would the farmers have hovering wagons, but still do all the reaping by hand with scythes? That doesn't make any sense. You're in a universe with spaceships and laser guns, but you don't have a tractor...and again, the harvesting montage could have been about half as long and still made the point.
I watched it all the way through and at the end they sort of shoehorned in an opening for more films after a "tragic" loss that seemed to lack any real emotion or impact.
Overall, the action in the last half is not too bad - if you check your brain at the door. It's enjoyable enough for easy watching while you're doing something else since the story is so predictable and simple. In all honesty though, it's better than the first film which lacked any consistency or even attempts at character development.