Merlion said:
Hmmm....it looks like a bit more to me than that. And I havent seen that many alternate D20 magic systems...especialy not good ones which I think AU might well be.
Count me in the eventualy buying both camp 
What more do you see compared to, say, Wheel of Time?
New classes...check
New races...check
New high quality magic system
with scaling spells...check
Assorted Rules variants...check
Tied together with a campaign setting...check
No elves...check
Usable alone or by borrowing interesting parts...check
So far, the only thing that makes AU qualitatively different is that it's OGL and will get better support both in-house and 3rd party.
Once could do a roughly similar comparison against Slaine, Sovereign Stone, or Swashbuckling Adventures/Swashbuckling Arcana as well. Furthermore, all four of these examples provide nice (and distinct) alternate magic systems.
Out of the five I've mentioned in this post, I'd personally go for Arcana Unearthed last. From what I've know so far from the design diaries, the other three are a little more to my taste. It seems from the ideas presented so far like the races and classes are trying too hard to be different. I like things that resonate in some way with various archetypes and images that I already have in my cultural awareness. None of the AU stuff hits me for some reason.
In addition, the design principle is to create the rules first, and then mold the creative ideas around the rules. Example:
http://www.montecook.com/diary.html The game mechanics seem to stick intrusively out of all the ideas like the haunches of a starving cow. Of course I understand that this is just a design diary and not representative of the final product, so I will wait and see. There's still a lot of fattening up for ol' Bessie yet, eh? In any case, should game mechanics generate the ideas, or should game mechanics flow from the needs of creative ideas? All four of the alternates I have suggested take the other approach, three of them because they are based on published works.
I do think it will be a really solid product, though, and I think lots of people will really enjoy it -- just not me. Who knows though? I'll take a look when it comes out and see what's what. Maybe I'll like it after all. I'd be really surprised if it was anything qualitatively different in concept from stuff already out there though.
