I love its form factor since I can bring it with my laptop anywhere.
The only other similar product I can find is the Headamp Pico DAC/amp.
Any recommendations? Volume knob is a must (rules out Fiio E17).
Leckerton UHA-6S mkII, Centrance DacPort, RSA Predator, iBasso D12, Meier PCStep (not released). The one that receives universal praise around here is the Leckerton, I'm having one now and it's pretty amazing.