I tested it with Isodynamic HiFiMan headphones, with 2-driver custom armature and with a variety of 1-driver armatures.
It really is way more interesting than any common DAC due to its different nature (the way that DAC works). All of the sounds are cleaner, because there are no peaks an the start of each sound - it starts as clear as it would do in a real life environment. That leads you to a better listening - you hear individual instruments more clearly, both in the bass, mid and high tones.
I can't really find any cons here - i was really amazed by that thing.
The only thing you might need to remember is that bluetooth is not capable of transmitting lossless codecs, requiring a double convertion, which is something you would probably want to avoid if your collection is mostly FLAC. I barely heard any difference to USB, but some people told me that they can hear it.
I don't really care much about accumulators' resource, so no comments on that.