I was deciding between the Dragonfly Black and the IEMatch (different purposes, I understand), but after reading all the good stuff about this, I decided to dive in and go ahead with the IEMatch. The long wait time for the local audio shop to stock up on the Dragonfly Black made the decision easier.
I am currently shifting from the FiiO X5 to my Xiaomi A1 for my portable setup, using the Heir Audio 4.ai s. With the A1, the hissing was extremely audible making it unbearable initially. Placing the IEMatch into the chain eliminated all hissing, even at high volumes, and I was impressed to say the least to finally have decent sound coming out of my phone.
But what really impressed me was pairing the IEMatch with my HiFiMAN EF2A amp and the Fostex T40RP. Prior to the IEMatch, my experience with the EF2A was channel imbalance at low volumes, but being deafeningly loud above the 9 o'clock level. With the IEMatch in the chain, I can finally turn up the volume without killing my ears, and even if I max out the volume on the amp, it doesn't get too loud. Happy with my rather impulse purchase, to say the least.