Rodney Thompson is getting back into the Dark Sun blogging game, and wrote a lot - mostly on tone of the the book, as seen by a original (1991) box-set purist.
Here are the most important quotes:

Athas is a desolate place where survival is not assured, where the very land can kill you, and where even the points of light (to use a 4E-favorite term) are ruled by darkness. It's a world of sword-and-sandal adventuring, of low tech and dangerous magic. It's a world where psionics is common, and where there are no gods to pray to or receive power from. It's a world where the land is struggling to stay alive, and its defenders face a near-hopeless task to keep it that way. Dark Sun is a dangerous world, a world of survival of the fittest, but...it's also a world for heroes. They might not think of themselves as such, but Athas is a place where evil rules so long as the common man does nothing.

Dark Sun is a setting that is zoomed in on a relatively small geographical area. There's a lot of diversity in that small area, but it's not hard to imagine world-spanning plots when the known world isn't much bigger than the American southwest. I also love the fact that the story of Dark Sun is about Athas, and that the focus remains on the world and not plane-hopping, god-fighting, or wars between extraplanar beings. It's about the here and now, the fact that death and extinction are very real things and that there's no such thing as divine intervention to save you at the last minute. Your fate on Athas is in your own hands, and while life may be nasty, brutish, and short...you also are the only one who can change that.

It's not a kitchen sink setting by any means; there are things that are part of other settings which simply won't be seen in the Dark Sun setting. There are also a few new things which fit the setting really well. Rich has already talked about the dragonborn a little bit (though he left out that we're also keeping the original backstory of the dray, that they were exiled from Giustenal and have a racial pathos about being scorned by their creator), so you know that some things won't be exactly the same. (emphasis added)

The sorcerer-kings rule over the city-states, using their templars as their agents throughout their domains. Savage raiders make the desert wastes even more unsafe than it already is. Giants wade across the Sea of Silt, staging raids on shoreline settlements and attacking passing silt craft. The Dragon still demands tribute from each city-state, and looms over the land like a force of pure destruction. Defilers destroy life to fuel their own arcane ambitions. Merchant houses still squabble amongs [sic] themselves, and wield a great deal of power outside of the sorcerer-kings' control. Mul gladiators still fight in the slave pits, and thri-kreen scouts lurk at the edge of rarely-traveled caravan paths, waiting to strike. Halfling cannibals still stalk the night like ghosts, and untrustworthy elves still lie, cheat, and steal from their victims in the Elven Market. The Veiled Alliance provides shelter from the authorities (and from the mobs of common folk who fear and hate them) for preservers, and they still fight defilers at every step. Ancient ruins filled with undead still lie in the deep desert, holding both danger and treasures of the ancient world.

The Full original Article is here