I was a supporter of Mystic Empyrean since it was a Kickstarter project and my opinion of it has not changed. Its main draws for me were its unique gameplay elements, but having reviewed the flavor of the world more in detail, I greatly appreciate the world that this game has created.
In Mystic Empyrean, you play as an Eidolon (basically a creature of pure magic) that gains powers based on your personality; for example, if you are prideful like a dragon, you gain powers from and eventually the ability to become a dragon. Your group moves throughout a land ravaged by the Aether trying to find "cornerstones" that restore lands, people, or concepts that the Aether has erased from existence. When a cornerstone is restored, the players get to choose what is introduced, thus allowing for a great deal of control over the world.
Player control is one of the key aspects of gameplay for Mystic Empyrean, since it takes the unique route of having no fixed gamemaster; each player takes turns acting as the GM for a round or encounter, while each other player gets an action. This cycling action emphasizes player interaction as it removes the possibility of one player dominating the play time. With no fixed GM, this also makes the world much more interesting since each player can create elements for the world that can be unlocked by new cornerstones. The rules to handle group participation and the creation of new content are both extensive enough to not be confusing as well as general enough to not be limiting.
I must also comment on the interesting core mechanic of the game: elements. Mystic Empyrean focuses on roleplaying, so each ability gives a general description of what it can do; for example, the first level of the "Dragonlike" ability reads "Scales and neck frills adorn the Eidolon's flesh, making him tougher and more resilient to the elements. He is taller and stronger than average, and may also develop claws and a tail, depending on the exact manifestations of the trait." This basically means that the player gains a claw and/or tail attack at minimum. If you choose to roleplay it intelligently, however, you could choose to use the cosmetic changes to your body to intimidate NPCs who fear dragons or charm those that idolize them - the focus is on the roleplaying, not the hard statistics. How challenges are resolved with these generalized powers involves the elements: each action corresponds to a certain element and each realm has a proportion of elements available to draw from. When you take an action, you draw from the realm's pool of elements and see how close your draw was to the intended element - the closer it is to the one you wanted, the better the result.
An example of an attack:
Let's say that a Dragonlike Eidolon makes an frontal attack. This action is tied into the Fire element, so the player draws a card. If s/he draws a fire or Anima (automatic success) something great happens - like a critical blow that defeats the enemy and affects his allies; if s/he draws an Air or Light (which are one step away), then it is somewhat successful - the enemy is hit, but could still be ready to fight; if s/he draws an Electricity or Darkness (two steps away), then it is a failure, but nothing really bad comes of it - you miss; if s/he draws a Stone, Water, or Aether (auto-fail) then something terrible happens - you get hit in response. The results are determined for story effect by the current GM. It is important to note that since each realm has a different set of elements, actions will have a different probability for success in different areas; for example, a peaceful realm with low Fire elements won't allow many direct attacks to succeed. This makes the players think more.
The game allows for a lot of customization of characters and realms, differing campaign types (combat, puzzle, or social), and is general enough for you to create even more abilities, items, etc. on your own (a community-driven forum also promises for opportunities to share your own ideas with the rest of us). Even if you don't feel like creating your own abilities, the book gives plenty of examples (90 powers, 100+ various items, etc. in the base book).
The one hiccup that may ruin the game is if you have a bad group: it would be easy for a rivalry to cause major problems. Of course, if you have a good group, then this game should turn out fantastically.
If you have a good group that can be creative and roleplay well, I know of no better roleplaying system that provides the elegance and fun that this game allows for.