What I liked best about the Scarred Lands was that it made an honest effort to develop this theme: The gods had to work together to save the mortal races. They succeed, and must
continue to cooperate to maintain their gains. What next?
This gives us the city of Mithril, a town run by somewhat stereotypical LG clerics and paladins. However, they have to deal with the corruption and survival issues of a frontier town. Furthermore, all of the gods have to be respected, even the evil ones. How do you approach that?
Hollowfaust, a city of necromancers who
aren't interested in taking over the world. They just want to learn more about an aspect of magic. People relocate there since they're powerful and fairly benevolent. The plainfolk live a good, if somewhat macabre, life. But the theme strongly flavors the laws and lifestyle. One of my favorites is that the bodies of those who die within the city walls become property of the necromancers.
Calastia made a good demonstration of a palatable Lawful Evil country. How a dictatorship could work without triggering a knee-jerk "must overthrow" reflex in the players. Having the weak service the strong with the strong protecting the weak makes sense in thier scenario.
Scarred lands took a Hellenistic framework and made it work. It presented a more polytheistic set of gods and explicitly, even heavy-handedly, made it so that the LG paladin could actually work with the CE berserker. Once the titan-spawn were cleared out, however, place your bets.
I think my favorites are the above city books along with Burok Torn, since it had an interesting take on dark elves, rune magic and alchemy. I also liked the planar book, but it was somewhat weak. There were a couple of books that addressed the Blood Bayou and the Bloody Sea, but I found that they fell short somehow. The Blood Sea one in particular was quite lacking. They're packed, so I can't give a more particular critique.