The players and the GM (me) for our current campaign love it. Since I invite a lot of player input, and let player character actions affect the world at large at Legendary Levels (80+) the players have had a lot to do with the setting.
However, things changed.
The players made a mistake, then followed the wrong trail, then ignored something, then lost the most important battle of thier Legendary careers.
So, we talked it over, talked about the fact I've been DMing for these guys for 7 years. That's awhile. That some of them have GM'd FR and other settings, but know more about our homebrew.
So, we decided what had happened to the world, how bad it was per section, and divided up the world between 3 GM's. Each of us took 2 continents and the surroundings.
In my area, the whole world has blown back to Stone/Bronze/Iron Age, with superstitious natives running around. There are Aztec/Incan/Bantu-like civilizations, and the old civilization that the world is built on the bones of was Egyptian Mythos, Roman Architecture, Japanese Customs, Minoan Dress. (It'll come in later more than now)
So, I did up my section, populated it, made the threats and problems, and since I finished first, I got GM first.
So far, the player's love it. They're mud wearing, loincloth waving, totem worshipping savages without a single social grace (One of them weilded a crossbow for 6 gaming sessions like a military pick because he'd never seen a crossbow) and while highly intelligent (some of them) they're REALLY IGNORANT!
So I guess I'd rate it at a 10. Sure, I've got a problem player or two, but we've been gaming together for years, and for the most part, we can pretty much get along and deal with it.
Of course, we kind of have a rough and tumble style of play that sometimes ignores the rules for the story/action, and has at times, involved paintball guns, bottles of whiskey, fist fights in the front yard, and once, a parakeet cage getting hit with a 5-iron and parakeet feathers exploding everywhere.
