Before post-modernism, when it was fashionable to talk about the 'great ideas' of 'civilization', monotheism was often represented as one of those ideas. And monotheism did indeed have significant benefits. It led to concepts of the universal brotherhood of man (siblinghood of humankind, if you want to be PC, I guess), universal ethics, etc.
OTOH, monotheism has also been responsible for ideological intolerance. In the Roman Empire, priests and adherents of a wide variety of religions coexisted peacefully. And yet, when Christianity become the official religion of the Empire, members of the same religion persecuted each other over differences on a single point of theology (e.g. the Aryan controversies).
Monotheism was also a force for political centralization and control. In Judah, when the people worshiped on hilltops and at local shrines, this was independent--one could almost say democratic--worship. But when religion was centralized at the temple in Jerusalem, power shifted into the hands of the king and the temple priesthood.
When you think about it, polytheism is an awful lot like the modern concept of pluralism. We may not say that we believe in multiple Gods, but our society freely accepts worshipers of Jesus, YHWH, Allah, Buddha, etc. Couples from differing religions will get married without feeling that one of them has to convert to the other's faith. In large cities like New York, Passover and Yom Kippur are public holidays just as Christmas and Easter are. All in all, the religious situation doesn't seem that different from that of the Roman Empire.
So was monotheism really a gain for society? Or was it actually a step backwards, taking us on a two-thousand-year detour away from pluralism?