I should mention that I wanted one of these when they were priced at $250, but I couldn't justify the cost. If you are curious about how this thing works, it simply plugs into your computer's USB port and has a headphone output on the other end. I plugged it into my MBP and it was automatically listed in the audio choices. I plugged in some headphones and selected the Dragonfly as my output and I was up and running. It features Asynchronous USB, which is to say that it is one of the best ways to get audio from your computer to your ears.
I have an old uDAC portable DAC/Amp that I bought for using on vacations or out on the deck in the backyard. I wanted to combine it with an iPad and it worked great with the CCK (Camera Connection Kit). The main downside was that Apple decided to limit the power of the USB port (or at least put up a message saying that the USB did not have enough power for the connected device) with a firmware update that tried to made it impossible to work without plugging it into a powered USB hub. I was hoping the Dragonfly would not have this issue, but it does.
While that is bad news, the good news is that with iOS7, it is possible to use the CCK with an iPhone. The question is how to use these without plugging them into a powered USB hub. I have found a way around plugging it into a power source, but it is a bit unwieldy. I found a device called "T3Hub" (if you want one, you may have to check eBay) that will trick the iPad/iPhone into thinking that it is being powered. It works great!
I should mention that I also bought a DragonTail. Since the Dragonfly is shaped like a USB thumb drive, it sticks out when it is plugged into a laptop. This can put stress on the connector and if it is bumped, it could break. I have three energetic pups around the house, so I would rather not risk it. The DragonTail is a 4.4 inch USB extender that is flexible and makes it less likely to mess up the Dragonfly. I had a Boxwave USB adapter that is similar, but it didn't work. Not sure if it was faulty or if there is some inherent issue with using it with the Dragonfly.
Personally, I don't usually comment on how something sounds because it is often subjective, (some like tube and some like solid state, for example). However, below are a few links to reviews that some may find interesting:
I should mention that Audioquest has come out with a new version of the Dragonfly that is priced around $150. Personally, I wanted to keep the budget under the $100 mark, so I went with the older version and I couldn't be happier. One thing that I like about the Dragonfly is that the dragonfly emblem changes colors when it gets a different signal. As an example, it is a pinkish color when playing 24/96 (see iPhone shot below), an orangish color with an 88.2 signal (see MBP below), and other colors depending on the signal.