*Please pardon any spelling mistakes. There are four vertical opaque bars going through my screen so I can't see all that I'm typing.*
I didn't read all the posts so I might be repeating what has been said.
I missed the gore. Stomach churning gore. Some scenes were pretty gripping and emotionally heavy but I just missed the gore. I understand they wanted to get a low rating so they could get a larger audience, but those tripods reminded me too much of the Striders (HL-2) and the harvester robots (Animatrix, the Second Renaissance Pt.2) where people were impaled and torn apart respectively. As most of the "action" was off screen the gore didn't even need to be shown directly. Maybe just a scene where the camera follows someone being pulled out of sight and then the sound of that person being torn apart or squashed. Maybe a shower of red. But of course the aliens needed people for asscandy.
Don't get me wrong, I'm not someone who thinks a movie isn't complete unless it has a high gore level. I just think it would have suited this movie.
Some other things:
"Oh, look at that, lightning just struck 26 times on the same spot. Well, you know what they say, lightning doesn't strike 27 times on the same spot. Let's all huddle around and see." That wasn't the only scene where people huddled around for the stock run-away-in-a-chaotic-and-frantic-way-screaming. Makes good cinema...if you're six.
Back to the gore, when the basket full of people fell on that tree wouldn't some of them have been impaled?
Supervan-Completely invulnerable to anything but an EMP (in case of EMP just replace the...the...euh...the thingy). Also has SUPER GPS which allows it to find a perfectly manageable path through downed aircraft debri and traffic jams.
Do fighter planes need to fly that low to be effective?
I swear, I thought it was the birds that made the aliens go dead

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Some things I did like:
Unlike some other other posters, I liked Fanning's performance.
The action was good. Not because it was so spectacular but because it wasn't in your face. However, the rest of the movie overshadowed it.