Since it's helpin', I'll defend my mild criticisms.
1. The "Don't use any rules but ours" insular nature (which is probably my BIGGEST gripe) is illustrated in a few places...the races are the first culprit with "only the bonuses and penalties described here," meaning that if someone is, say, an Aarakocra from Faerun and they meet an Athesian Aarakocra, they could be stubtly to wildly different. That fits somewhat in the flavor of the setting, but also at the same time limits it. I haven't extensively checked the mechanics, so I'm not sure how different they are. It's kinda like, yeah, Athesian halflings are different from any other halfling race...but what if I, as the all-powerful DM, like regular halflings and want to include them in the campaign? Are there going to be balance concerns? Am I going to destroy the flavor so much that the update teem says 'you're on your own, man. Good luck.'
It goes on with 'athesian versions' of basic classes (such as the Bard).....was the Bard really so bad that I can't play a PHB bard in Athas? Is a singing and dancing halfling too out of the league of Dark Sun to support? Also, the lack of certain classes (why couldn't the Sorcerer be adopted to the Athesian spellcasting method?) makes me wonder...
Monsters continue it. The Braxat in the MM2 is flawed in some way, I guess...because the 'athesian version' is the right one, for the world. Use another one, and it'd be like using bardic halflings or a gnome paladin -- inappropriate. What might be more useful, I would think, is telling me how to give what exists Athesian flavor, rather than telling me to ignore what exists and only follow these rules.
Weapons are symptomatic of it, too...that many variations on that many themes....why? I can understand a glut of strange exotic weapons for the gladiators (and would feel a bit left down without it

), but why would you need to whip up new weapon statistics for a jawbone on a stick that couldn't already be done with a greatclub or a greataxe? It makes me think that there must be some special significance to that, when none really comes accross in the information presented...at least, none that wouldn't also come accross with simply the note: "A carrikal functions like a greataxe made of inferior materials." In addition, this makes feats and proficiencies a bit wonky. If I'm proficient in a greataxe, why can't I use a carrikal? If I can swing a morningstar, why not an alak? Are they THAT different?
Maybe I'm asking too much though. Or maybe it's just presentation. That's entirely likely. I'd just like maybe a sidebar, an entry, SOMETHING on what to do with the basic PHB as it is, and how one may integrate that. I guess it's the whole 'options, not restrictions.' While I understand that a campaign setting has to have some restrictions, or else loose it's flavor, advice or a minor alteration on the races or classes seems much more useful to me than rewriting the book with 'em.
2. Preserver/Defiler distinction. Well, for starters, I'd like something in the
class description telling me which class I am. It's kind of along the lines of "for my class, I'm a wizard..." and the class description specifies nothing beyond that. They mention the defiler/preserver dichotomy, but they never say one must choose in clear, defined, rulespeak. I could make an Athesian Wizard and the only rule the document tells me I need to know when making the class is that my spellbook should be concealed. You'd think if there were game rule changes to what a wizard would have to do, they'd be listed under game rule information....? I mean, it's probably there, but it's hardly clear cut or definate, and I still don't know if I may be missing something....do I say I'm a Preserver and then just not have to deal with the defiling? Or vice-versa? Or is there a feat to take? Do they mutli-class? Or do all 'wizards' use one or the other? It's a stumbling block to understanding what is a fairly fundamental change in the rules.
In addition, the Arcane Magic area, which seems to be the perfect place to list this info, has terrain modifiers for defiling and info that Athesian wizards are either preservers or defilers, and that preservers risk temptation by the 'dark side,' as it were. Nothing on the choice, nothing on the dedication, nothing on the damage.
3. Feats. Specifically, I'm referring to the Freedom feat, which basically gives someone a big advantage that it takes about a second-level spell to duplicate (compare to Haste, which does basically likewise, but adds more...so take away those random Haste bonuses, and still keep the extra action...1st-2nd level spell). It'd be like saying 'because you're from City XYZ, you can gain the ability to cast Magic Missile once per day.' And honestly, just a few quesitonable things like that raise questions about everything.
4. Terrains. I guess....the main question I'd have is that are rocky badlands really that different, mechanically, than 'desert'? Or salt flats? It's all well and good to add this new richness, but it clunks things up a little bit, and invalidates the 'default' rules. I could see it on the monsters, maybe under geography....but would there really be a pressing need for the difference between a salt flat and an obsidian plain? Both are big chunks of burning something, endless to the horizon...is there a NEED for that added complexity? I think in the monster descriptions, and geography, maybe...but to have greater rules effects puts me off...
In Closing: Again, I must thank the team for the hard work they put into it. Like I said, it's definately more good than ill, just a few things that glare at me the wrong way.

I like it, and I thiank you.