I am a Best Buy employee and I've been wanting a Dragonfly for a while now but never pulled the trigger due to lack of support for mobile devices. I never really listen to music from my laptop; it's always from my phone using headphones or in my car. Audioquest revised this device for customers like myself.
First off, I've had this for about an hour now and it took me a bit to start noticing the benefits. I'm currently using this on an S7 Edge with some V-Moda M-100s. There have been a few issues getting my phone to recognize the USB device. I'm running Spotify Premium and the first several times I plugged in the Dragonfly the music was super digitized and there were no highs. It was all bass and sounded like 16 bit music. I researched the Audioquest site and there will eventually be a firmware update client for the dragonfly, but currently the website says "coming soon." So that was no help.Through some more research on Head-Fi this is apparently an issue with Android Marshmallow. It works fine on Lollipop and iOS devices, but until Marshmallow gets an update, the USB audio support is finicky. The dragonfly does work on my phone but sometimes I have to unplug and re-plug it several times, or have a song already playing when I plug it in to get it to work. Incidentally, it has worked 100% of the time on my laptop.
As for sound quality, as I started to say, I did notice a difference right away, but I didn't notice how vast it was until I switched back and forth from the DF to the headphone jack several times. Each time I used the phone's built in DAC I felt it sounded more and more flat and closed off. The soundstaging with the dragonfly is vastly better in comparison. It wasn't mind blowing, but just so much more preferable than what the Samsung built DAC was putting out. Like I stated I use Spotify Premium which gives me access to 320kbps mp3s, and I don't have any lossless music to test. I may migrate to Tidal which is a lossless music streaming app. I've had it previously and LOVED the audio quality but was not satisfied with the performance of the app itself. I can't wait to try my dragonfly in the car, even though the quality difference won't be as noticeable. The best way to use this device is with headphones or through a good home theater amp and great speakers, playing some lossless music like FLAC (no mp3s). So far I am extremely happy with my purchase and I haven't even put it through it's paces yet.
Any music fanatic, or even just a casual listener should love this product. There is also a new Dragonfly Red that uses a more advance DAC with higher power output and a more controlled 1 step = 1 decibel volume control