One of the most well thoughtout settings I've ever read. There are only a few races on four worlds, but all of them are given deep cultures and complex histories. The core worlds are very distinguished too, but also build around common themes and ideas, that hold the cosmology together. They tone is very grey, even though the gouvernments are shown to be corrupt or in a state of corruption. Which means, that this universe it the perfect place to play heroes and villains, who will change the course of history.
The Setting delivers a lot of ideas for adventures and campaigns and the archetypes of known classes read interesting enough. I also like the idea of cutting clerics out of the setting and give bards more ways too shine.
My personal point of critique though is, that there's onlyone Archetype for Paladins, which is my favorite class in Pathfinder and D&D. The kinetic knight does read fun (like a Jedi only using his mindtricks), but I'm more a fan of knights in shinning armor. I would have loved more descritptions or ideas what makes a paladin different in Aethera, especially since paladins still use clerical magic.
Besides that, I sincerly hope that the designers are still working on the setting and that there will be soon conversions to 5e and Starfinder. Since this is already the case for supplements, I'm quite hopeful. It would be a shame, if the Starfinder campaign setting would have a monopoly on science-fantasy rolepaying games.
[5 of 5 Stars!]