We sell a lot of DACs here at Shoreline. I'm a big fan of all of them. But I can't think of any that have received the widespread praise and instant success of the Audioengine D1. Most new products take 6 months to establish themselves, but within weeks of the first D1s shipping, we couldn't keep them on the shelf, and we had a long line of folks waiting for the occasional open-box return. Just like the K&K Pure Mini, it's ultimately irrelevant what I have to say about this product; the customers have spoken, and they love it.
Nevertheless, I will add a few comments. Perhaps the most striking design feature of this unit is the black box + one knob simplicity of it (much like the Audioengine N22). Sure, there's a few inputs in the back, but this USB-powered DAC is meant for easy use and zero learning curve. For an inexpensive DAC, the performance is out of this world. Great imaging, expanded tone, all that you expect from a good DAC. I recommend it without reservation.