If you go into Battle: Los Angeles looking for Marines vs. Aliens or Black Alien Down - crazy urban combat with hearty hoo-rah jarheads battling weird mech-aliens - then you're pretty much going to get your money's worth. It's crazy, frenetic, shaky-cam chaos with almost non-stop action and mayhem.
Where the movie stumbles a bit is in grafting on a truckload of war movie cliches: Staff Sargeant Aaron Eckhart has already had his retirement papers signed when he's called upon; one platoon member is getting married; one's a virgin; one's from Nigeria; one's brother died on Eckhart's command and thinks it's his fault; and so on. It really feels like the studio ordered up some tropes as if we were going to be able to tell anyone apart once the booming starts and feel something when they buy it. Other than Michelle Rodriguez as the ditzy, blonde Valley girl...just kidding, she's a kickass Latina Air Force intel officer like she sort of was in Avatar, Eckhart stands alone as having a "character."
While the dialogue breaks are frequently rote and predictable, the action manages to be something special for being epic in scale while intimate in detail. We're going to have to wait for the next Transformers movie this summer to get the Bayhem-grade boombitty, but this is plenty asplodey enough.
Score: 8/10. Catch a matinee on a big, loud screen.
One quibble with the plot (not really spoilerish): It is theorized that the aliens are here to steal our water. OK, the surface of Earth is 70% water - why not just land in the middle of the ocean and take what you want without having to blow up the locals?
Also, I think of lot of the negative reviews have come from angry liberal critics who can't stand the idea of American military being portrayed as brave, resolute and heroic. After years of anti-Iraq/Afghanistan war movies that have smeared soldiers and bombed at the box office, they fear this movie being a hit will lead to more movies being made with heroic warriors and are trying to dampen enthusiasm. What babies.
Another thing: Would it kill Hollywood to show a Lieutenant who isn't some book-learned recent graduate of the service academy who is immediately in over his head and needing bailing-out by the veteran sergeant? Yeesh, it's Lt. Gorman from Aliens all over again.