I have had this amp for just a couple of days, but it has made a very good impression on me. I bought this second-hand to be used alongside with a computer and maybe as a travelling amp (haven't tried it yet).
The connectivity of this amp is superb - you get DAC functionality via USB/toslink/coax and portable amping from 3.5mm jacks. AFAIK, USB DAC is 16/48 and optical/coax is 24/96. I have not yet been able to play 24/192 FLACs via ASIO from my computer, btu it may be just some configuration issue I haven't figured out yet.
The size of D1 is great for a desktop amp but less than exciting as a portable amp. I would have to put it in my shoulder bag - there's no way I could fit this in any of my pockets comfortably, even though I use cargo pants regularly.
The iBasso D1 has no trouble driving my AKG K701. I haven't had the need to turn the vol.pot past 11 o'clock. If I would plug in my Koss PortaPros with the same volume setting I used to drive the K701s, the PortaPros would probably rupture their diaphragm. Too bad there isn't a gain switch in this model.
The fake leather cover doesn't look very nice but it protects the case when I'm on the road.
For the price I paid for it (108,50 euros), it's a great bang for the buck
Update: I'd say the soundscape of this amp is average. Compared to an audio store's setup of NAD's 500 euro CD player and some black Musical Fidelity's (if I remember correctly) HP amp, the iBasso loses. It is still a huge improvement to a PC's stock integrated sound card.