Specification wise, it's not that "great". In terms of reproduction, it outputs a more neutral and pleasant sound signature with much better vocals, sound stage, and instrument separation. It is one of the best, if not the best op-amps i have found to date (surpasses second place LME49990 by a fair margin in my opinion). It sounds a little closer to a V sound, where the mid-range vocal is a bit more centralized than the other bits and pieces of background music. I prefer this, but audio is an iffy hobby so where one prefers, another can dislike.
It has an internal power supply that regulates clean energy, separate volume controls, op-amp based for sound design, runs cool, great DAC IC's, and a pretty darn good multiple layer pcb to save room. Only negative i see about the Essence One is that it takes some time to tweak the sound the way you like it. Having that said, the output current is a little low and may only satisfy a few planar magnetic headphones such as HE400. I felt like the HE500 and LCD2 was super restricted, but hey, take my opinion with a grain of salt.