Got my Dragonfly last week.
Compared to the headphone out on my iMac, the Dragonfly sounds much fuller with better bass and a wider soundstage. I have only tried it with my JH Audio 16's and then with some cheap earbuds when I brought it to a friend's house. Even with the cheap buds, my friend and I both easily heard the improvement over the headphone jack on her laptop.
Great little device.
One neat thing I've also noticed with the Dragonfly is when I use Pure Music (up sampling off) and I select a track with a different bit rate, the Dragonfly will do a quick fade out / fade in between tracks rather than a click or pop that I get with some other brands of DAC's.
Nice!