I have the .pdf of AU since I am doing some proofing of Siege on EbonRing. And while I haven't looked through the entire .pdf document of Arcana Unearthed, what I saw was quite nice. The ability to play a flying faen (spryte) is something I've wanted to do for a long time. Now, if I can just convince my group to give it a whirl.
And the cool thing is, it's like totally portable to D&D. I mean, you could rip out all the classes and plug them in right beside half-orcs, gnomes, and dwarves without breaking a sweat. That's the coolest feature, IMHO.