Movie is a bit long and the actors do a good job given what they're got to work with.
Let's be honest, you're not going to see this for the acting. You are going to see this for the sheer spectacle of the earth's destruction. On that point, you wont' be disappointed. The combination of visual and audio effects is amazing.
Should you see it? Yes, but do so while it's showing in a large auditorium with a good sound system. Do that and you'll get what you paid for.