I've got to be honest, I didn't really like it when I first saw it on video back in the 80s or 90s. I had just come off of watching the Dollars Trilogy and wasn't really prepared for the change in style. Of course, now I love it and think it's Leone's masterpiece, but I had to watch it a second time to really get it.
The film's relative lack of success in the U.S.A. and major success everywhere else is the reason why Bronson was considered a superstar in Europe but didn't really become a screen icon for Americans until Death Wish. He was already past 50 at that point and didn't have too much time left to capitalize on it.
I've seen this many times but the most recently, I was not as impressed with the opening scene as I used to be. This time it struck me as self-consciously "arty" with each of the killers performing these weird little routines as if they were in some obscure French absurdist film instead of a spaghetti western.