First, the good. The battle scenes are very good. They are action packed and lots of stuff blows up. I also liked that the aliens, while they have superior technology, they don't have a "super weapon" that wipes everything out in one fell swoop like in Independence Day. Also, they didn't get into the American moral superiority like in Battlefield Earth. That's a definite plus.
Now, the bad. Everything else. You can't start with a character/morality movie, abandon it after 15 minutes in favour of action and then try to salvage it at the end. All the stuff at the start about the soldier's lives was unnecessary and never got resolved. So lose it and make a decent action movie. Second, shaky camera work is never necessary. In trying to make it seem real, all you do is distract the audience from seeing the cool things like explosions and aliens. And it isn't realistic. The human eye compensates when the body is in motion but it can't anticipate and react fast enough when watching film. Third, Aaron Eckhart + Michelle Rodriguez = bad acting. The acting all around is just not good. Fourth, the military strategy wasn't well researched. Even I know that, in a situation like that, the raised freeways will be impassable. Everything's being blown up after all. Finally, I'm not sure why they felt there needed to be a closet romance between Freddy Mercury and one of Theo Huxtable's friends (it may be worth watching just to find out what I'm talking about).
See if you like battles and stuff getting turned into rubble and don't have to pay more than $3. Otherwise, just watch Independence Day again.