This is a great movie. I stumbled upon it in my quest to see all of the "1950's SciFi" movies. I was also drawn to it since the great Terence Fisher directed it.
The plot about a group of people trying to come to terms with an alien invasion has been done before and done since however for what ever reason this film just plays out fantastically well.
Certainly its no better or worse than many other films in the genre, but during the 60 odd minutes that it unspools it holds with rapt attention, something that many other supposedly better films fail to do.
I know that once seen it may fall from memory but while it may not remain foremost in your brain it will forever spring up when you see the title with a "Hey that was a really good film".
If you can see it, preferably late at night with all of the lights off.