Rachel is either adorable, The Woobie, and someone you can't help but feel sorry for, or just an annoying brat and The Load who screams too much. Others feel that the character as written might have been annoying (and was possibly intended to be played by a younger actress), but Dakota Fanning's performance was good enough to redeem her.
Robbie is viewed as either impressively brave or just plain stupid.
Catharsis Factor: After an hour and a half of the aliens mercilessly slaughtering people without taking any damage, it is extremely satisfying to see Ray blow up a tripod with a belt of grenades, followed shortly thereafter by the military blasting one to pieces with Javelin missiles after its shields go down. Similarly, it's pretty satisfying to watch the aliens stumbling around sick and dropping dead due to their lack of immunity to Earth's pathogens.
Faux Symbolism: When Ray and Rachel arrive in Boston, one of the first things they see there is a statue of a Minuteman covered in dying alien weeds.
Glurge: The ending. Despite taking arguably the dumbest course of action at every possible turn, the entire family somehow survives and happens to reunite at the same spot at the same time. Doubly inexplicable for Robbie, who spends the entire movie trying to get himself killed.
Inferred Holocaust: During the course of the film, the implication is that a very sizable proportion of the human race has been exterminated and much of the planet has been laid to waste by the invaders. Yet with possibly millions, if not billions of people dead and the Earth in ruins, one gets the impression we're supposed to find the ending in which the family we've been following all somehow survive and reunite with the motherto be a happy one.
Some of the imagery is reminiscent of the actual Holocaust, such as victims' clothes falling from the sky, invoking ashes from camp crematoriums falling back down to Earth like snow.
Jerkass Woobie: Ogilvy starts out as this. He's not a nice person, but he's a man who's just lost his entire family, combined with watching the world get taken over by aliens. He loses sympathy as he becomes more antagonistic toward Ray, to the point of not caring if he and Rachel die because of him.
Moral Event Horizon: The aliens cross it by attacking Earth and going on a planet-wide genocide.
A three-year old TySimpkins briefly appears at one point. This was his first film role.
Rooting for the Empire: As terrifying as the tripods were, let's face it: Several viewers rooted for them after finding the humans annoying.
Shocking Moments / Big-Lipped Alligator Moment: One scene, a clever nod to the original story, involves a crowd of people, including our protagonists, walking through town, when a railroad crossing signal sounds. Everybody clears the tracks as the gate comes down. Then the train passes. It is on fire. It leaves, the gates go up, and it is not commented on by anyone. Roger Ebert, who gave the film a mixed but mostly negative review, called this scene "unforgettable".
Squick: While Ogilvy's interest in Rachel may be that he sees her as a Replacement Goldfish for his own daughter, some viewers found it disturbing, and Ray is clearly concerned by it.
Ugly Cute: The aliens' real appearances (i.e., notthe Tripods) are weirdly adorable when we actually see them.
Robbie for blindly charging into battle when he sees the US military already being slaughtered, and he's not just a civilian, he's a kid. Nothing he was doing served any other purpose than getting himself killed. (almost)
Rachel to a lesser extent. She may be just a frightened child, but her ear-piercing screams and decision to run out of the house in a panic serve to very nearly cost her her life despite all of Ray's efforts.
Manny, the mechanic who was too busy chewing out Ray for commandeering a van parked at his garage while there's a massive panic unfolding all around him as the tripod approaches right behind him. Ray even says flat out he's gonna die if he doesn't shut up and get in. Sure enough, that's exactly what happens to him.
Special Effect Failure: While the quality may be up for debate, the quality of the effects is not. The heat-ray was straight out of a '90s video game, the tripods clattered along independently of the surfaces that they were standing on and the nighttime was represented by superimposing starry night sky over some of the visible blue afternoon sky while being filmed in bright sunny daylight.