OK, so let's get the bad out of the way first. Like most alien invasion movies (or TV series like Falling Skies, which this movie most resembles), Battle: Los Angeles makes the most fundamental of errors; namely ignoring the fact that any alien race advanced enough to send an armada over interplanetary (or interstellar) distances, would be technologically as far advanced over us as the US military would be over Amazonian tribes in dug-out canoes armed with bows and arrows. But no! The film makers equipped these aliens with small-arms, armoured support and aircraft broadly comparable to the human equivalent. That's just plain stupid. The pitched battles and house-to-house fighting is pretty evenly matched and if the enemy didn't have long spindly limbs, bulbous heads and weapons that make a VUUUUUUUP! sound instead of BRRRRRRRR cak-cak-cak! you might as well be watching any urban warfare scenario. The aliens are also annoyingly inconsistently difficult to kill - in one scene it takes several seconds of automatic fire at point-blank range to kill one, whereas in the next, they are being picked off at range with single shots.
But I suppose any sci-fi demands that the viewer suspend their disbelief, so I'll nit-pick no more and get on to the good stuff. In terms of eye-candy, Battle: Los Angeles is superb. The CGI is well above-average and the alien hardware pretty damn awesome (most notably the final assault on the alien command centre). The shaky-cam effect is used to good effect (and thankfully not over-used) and the action rarely lets up. 5.1 sound is exceptional - if you have a decent home cinema system, you're in for a treat. There's tension aplenty and some decent enough acting - the kid 'Hector' was remarkably credible. Although a few American war move clichés will be spotted by the astute, it's also a tad less gung-ho and irritating than Independence Day.
All in all, if you get a few beers in and leave your brain at home, Battle: Los Angeles provides reasonable entertainment and will give your HD home cinema system a decent work-out. Worth a look if you don't expect too much and don't analyse your sci-fi too deeply!