This movie seems at first like it's going to be the stuff of Mystery Science Theater 3000. It's basically something bad but amusing that you can make fun of. The supporting characters and extras, especially at the beginning, are just atrocious actors. But instead, the movie transforms into something pretty awesome! The end of the world feeling throughout is great, with a vast wormhole sucking up everything around it.
But then other times it's like Dukes of Hazard, with sliding off hoods of cars and vehicles exploding after getting no more than a fender bender. The movie is out of control, careening between amazingly excellent and complete crap. It's like some wise Hollywood producer said, "Needs more action" so they stuck in the most tired, cliched action sequences you can think of: car chases and gun fights. Neither belong in this film.
There's also some implausibilities. For example, David, a guy from the Navy in 1943, inexplicably runs from the Navy of today. Why would he run from the men he should trust the most? It makes no sense. Furthermore, the Navy of today is often shooting at him with real guns! Why would they be trying to kill a man who has done nothing wrong?
Anyway, it's an enjoyable film despite the inconsistencies.