A great, well built, great sounding dac with class A amp.  Nice analog volume pot, nice form factor, nice build.  Output impedance is a bit high for a portable, at 10 ohm.  Centrance will modify it to 1 ohm for a mere $100.  I have not bothered.  My headphones are 80 ohm, so they barely meet the 8x output impedance rule.  I always use my Pico slim between my dacport and my iems.  Nice piece of kit, but pricey - my only complaint.

First - I bought mine used - my complaint on price is based on new price of $400, though I guess it holds value...   OK, that's out of the way.  Justin at Headamp builds some of the highest quality hardware I have ever held in my hands - truly beautiful.   Sound quality is outstanding - close to wire with gain as I've heard.  I have yet to run the battery down before I get around to a recharge.   The volume control is second to none.  If you listen at low volume levels with sensitive headphones and iems, the Pico Slim is the best there...

I love them - great sound, a detailed, slightly warm, non-fatiguing sound signature.  They are very portable, cool looking, well built.   I tolerate the lack of comfort and the fact that they are quite sensitive, and leave most amps with very little volume travel.

The quads sound fantastic to me.  They are my preferred sound signature - all the detail, very present bass, but honestly not fatiguing or overpowering, very slightly attenuated treble.  All this leads to a detailed yet warm sound, and the slight roll off on the treble keeps them from being fatiguing.  These are concieved as a stage monitor first, and as a high end pair of headphones for musical enjoyment second, which always works well for me.  So many "audiophile" headphones have some sort of built in "wow" factor somewhere in the frequency band...

The perfect traveling companion, and my first high end amp.

Review at this link:   http://www.head-fi.org/forum/thread/511909/headroom-ultra-desktop-review#post_6924768   In Brief: A brilliant amp and Dac in a brilliant form factor.  I've wanted this amp for 3 years; I am not disappointed!