Science Marches On: At the very least, there's no Martian civilization invading Earth, and much of the speculation about how the Martians' technology and biology works is based on outdated science. Wells does future-proof the story to some extent, though, by constantly stating that the characters' scientific speculation is just that, and they could be entirely wrong.
In some ways that makes our technological advancement over the last 100 years or so quite scary. These machines were pretty much the most deadly things that the author could think up, and yet put them against modern weapons and they would be obliterated in seconds.
The Martians' main advantage is that their weapon is point-and-shoot accurate, whereas artillery of the day required that the target be 'bracketed' in order to reliably place fire on the target. So the artillery would open up with their initial shots to try and find the range, and the Martian Heat-Ray would immediately and accurately destroy them. The Thunder Child was so effective because it closed to point-blank range before opening fire.
Also because it was by no means clear to the Martians that this iron ship was anything to do with the humans, or had any aggressive intent.
The Martians are described lacking a true digestive system, instead draining blood from other creatures and replacing their own with it, thus gaining the necessary nutrients. Needless to say, the understanding of blood transfusions hadn't developed very far when the book was written. And there's also the issue of No Biochemical Barriers, although they did all die from interaction with Earth's ecosystem...
Technology Marches On: The awe that the humans experience upon seeing the Martian flying machine is somewhat dated, especially considering that human flight would be achieved within the next 5 years. In contrast, every other piece of technology the Martians use has aged surprisingly well, as walking machines and directed energy weapons, though beginning to appear in real life, have yet to become subject to the industrial precision and mass-production shown in the novel.
The scene where the protagonist describes the Martians' aluminium refining technology. A modern reader may think "So what? Big deal". At the time the book was written, however, aluminium was extremely difficult and expensive to mass-produce, it was even considered to be a precious metal with a higher value than gold, so being able to mass-produce it was used as proof of the Martians' technological mastery.
Even then, today mass production of aluminium isn't exactly cheap or easy, at least not compared to something like iron. It's cheap today in large part because we recycle it far more than we do other metals.
The mass panic associated with the radio broadcast? Not as massive as we've been led to believe, but not entirely faked or over-reported, either. Most people would have reacted as most probably would today: call the police or friends and find out. CBS got an unusually high volume of calls, as did police and fire stations, so people were trying to verify one way or the other. Caches of letters to CBS, Welles and the FCC have been found, from people who had believed it — many congratulating Welles for a job well done. The listening audience size was six million, and it's estimated that about a million of those, however briefly, believed the program. (Because it was Halloween, some stupid things were bound to happen anyway; a lot of extreme reactions came from people who hadn't heard the show, but heard of a "Martian invasion" (or a "deadly meteor crash") from friends or neighbors. Others who thought it was real simply tuned in late, heard "invasion" and "poison gas" and thought "Nazis".
The idea that a lot of the panic came from people who'd switched over late from The Chase & Sanborn Hour is based on the fact that Chase & Sanborn was "lowbrow" comedy with Edgar Bergen and Charlie McCarthy, so researchers assumed that anyone who believed in a Martian invasion must be dumb or naive. Letters and telegrams revealed listeners who'd had CBS on as background noise; others were fans of Mercury Theatre who had tuned in late or didn't hear the first couple of minutes and thought Mercury Theatre was being interrupted.note The fact that Mercury Theatre had just had a time-slot change, plus an erroneous newspaper listing that Welles and co. were doing "The Pickwick Papers" that night, didn't help. Still others were listening on faraway static-ridden stations and could only hear parts of what happened. Many heard "invasion" without the "Martians" which would have told them it was a play. Others heard "meteor crash" and thought it was a natural disaster. Brad Schwartz in his book Broadcast Hysteria writes:
Above all, what late listeners heard and understood were the references to real organizations and figures of authority. Their ears pricked up at the mentions of the governor of New Jersey, the Red Cross, the vice president of CBS, and Princeton University. This, more than perhaps anything else, made the broadcast seem real to those that it deceived.
Welles was deeply involved in producing a theatrical play at the time and was only peripherally involved with the preparation for War of the Worlds; but he emphasized that it must be as realistic as possible because the story was an old classic and he feared listeners would be bored and tune out.
Science Marches On: While preparing to make the movie, producer George Pal talked to military representatives who let him know in no uncertain terms the tripods of the original novel would be cut to pieces by modern weaponry before their drivers would suffer so much as a sniffle. Hence the movie Martians came equipped with nuke-proof force fields.
The 1953 movie opens with the narrator explaining why none of the solar system's other planets were suitable for invasion, and getting most of his information completely wrong. Which is kind of a shame, because the shot of erupting volcanoes on Jupiter is pretty well done for the time.
What Could Have Been: Ray Harryhausen apparently always wanted to take on the story, but never got the chance to do so.