I have had an audioquest DragonFly Red for a while now and it is my required travel companion! Originally it powered my AKG K550 reference headphones that I loved for travel because I got great sound in a fold-flat(-ish) form. The DragonFly gave so much more to the headphones that I used it for music and movies on flights and hotels. I swapped out the AKGs for my Shure SE846 in-ear monitors and the combination of the DragonFly and 846 was amazing. The sound isolation from the 846, with the power and clarity of the DragonFly means I can listen to music or watch a movie on my iPad on an airplane with more clarity than any noise cancelling headphones I have heard, all while still with the iPad volume at about 30%.
So, the moment I heard audioquest was updating the DragonFly series with the new Cobalt, that $299 upgrade was a no-brainer. I have to say, of all the audio equipment I have, the audioquest/Shure combination is in many ways the most indispensable.