When I saw it as a kid, I didn't understand the premise of the story, and as an adult, I still have problem with the premise that a runaway missile from space starts to circle around the earth by sheer chance. I guess that's what makes this movie one of a kind. If you go beyond the incredible coincidence that this missile just happened to find earth and randomly started killing its inhabitants, the movie is pretty good sci-fi from the '50s. They try to make things look factual by using stock military footage, and use pseudonym of actual existing institution like Havenbrook (which is an obvious reference to Brookhaven National Laboratory).
The scary part of the movie is the glow you see over the horizon as the missile approaches, and the sound it makes. The movie is somewhat leaning towards horror genre in this respect, and what happens to the main protagonist as he attempts to stop the runaway missile. If you've seen this movie once, you'll never forget it - which makes this movie one of the sci-fi classics from the '50s.
If you can find it (as it's getting easier with so many posting of old movies on the internet), this movie is worth a glance.
