I love this film aswell, and I love it's wonderful score by Morricone
This is a much more sad and bitter film, as opposed to the Dollars-films who had mostly a lot of sardonic humour.
And to me it feels more like a true spaghetti western than OUATITW did.
Steiger is overacting many times, but it doesn't matter I think. Wallach did the same as Tuco, it's just how the characters are meant to be.
It's a great buddy movie, as Tom B says in his post above.
As a political western it's also a bit different to the others, lacking the simple naive messages they often had.