I guess I'm the only American who never watched "Full House", and thus I have no impression of John Stamos from that show. Here, he's a little bit overly aloof/cocky, but really, is this supposed to be a hard-hitting war documentary? No, it's supposed to be a little bit historical with some war/action scenes but mostly just light fun. It manages to do all of that pretty well. As other reviewers here have pointed out, it never drags. It isn't always realistic, but the implausibilities aren't severe enough to ruin the fun, and there is a decent sense of real danger during the war part.
One thing I liked was the overall feeling of the 1940s; they did a good job with that for a casual comedic movie, IMO. Also there are some genuinely witty bits of dialog here and there.
I give it 5/10; it's nothing special but it's a pleasant way to kill 90 minutes.