The system is built strongly into the setting and vice versa; it's hard to un-marry the two. The setting feels like Fantasy Greece and China had a baby. Powerful entities that are quasi-demigods like Hercules stomping around dealing with big issues, be it divine turfwars or, well, anything.
The idea is that instead of atoms, magic is the building block of everything, and that magic is called Essence. Solar Exalted (and other entities) can basically manipulate Essence. Essence is also a real thing, and people use it (A prayer, for instance, is a tangible thing that holds power, and is also sent to the god it's being sent to).
They definitely take a page from Chinese religious mythology; Gods literally are in a bureaucracy. Prayers = paperwork. Each god has a domain, and then you have a chain of command or a hierarchy over that, down to a god in charge of cooking fires of that block over there (if you wanted to be specific). Of course, this hierarchy is messed up in the current age, with things either neglected, or gods overstepping their bounds and gobbling up things they don't deserve. I loved the fluff so much, I'm co-opting it for my 4e game.
When it comes to mechanics, I definitely like it. There are powers that also facilitate social things. For instance, a power (Charm) that lets you look into someone's heart, and find out the one thing that if you could give them as a bribe, they would do what you wanted. Another, a Bureaucracy charm, can shut down a government's activities, or speed it up to accomplish something you need. It's very fun and evocative.
Another nice aspect, when it comes to character creation, is that it's pointbuy. And while there are "classes" in a sense, it's very easy to "Multi-class", if you will. A Wizard (or Twilight Caste) can easily be just as good in an area like Archery or using a Sword as a Fighter (Dawn Caste). Except that the Dawn Caste has a much larger breadth of choices (Dawn start off with "Proficiency" in Melee, Brawl, Martial Arts, Archery and Thrown).
The power level is definitely a change. A fresh Exalt is roughly on par with a 12th level PC in D&D. However, there are definitely some differences in the system. There's barely any healing magic, and next to no ressurection. Also, MAGIC (or Sorcery) is a whole different kettle of fish; there are only 3 levels of Sorcery, and even the lowest level would be on par with Stone Skin (or cause effects like making a square mile instantly produce harvestable crops and impregnate/force birth all livestock in the area).