It's an all-time classic. It's considered the best of the 1950s flying-saucer movies. I've lost track of how many times I've watched it since I was a kid in the 60s.
I really liked it. I saw it in the early 80s at a time when there was a lot of hype with Sci-Fi entertainment (Star Wars movies, V: The original Miniseries, etc.) and found fascinating that the phrase "Klaatu barada nikto" was incorporated into 3 characters from Return of the Jedi.
It was a great movie and infinitely superior to the Keanu Reeves version. It's message still stands up today. It was very original to have all the electricity on the planet turned off except for a few exceptions, planes in the air not being harmed. While the ending is a little open ended it is more than satisfactory as it leaves the choices to human beings. Who doesn't like Gort?