Got some time in today with the DA-8 - pretty impressive so far. A few observations:
*The headphone jack is a tight fit. Not terribly tight, but tighter than average. They even mention this in the manual, and say to make sure you plug in all the way.
*Good power on the headphone out. I ran an LCD-2 and a Thunderpants to satisfying levels and felt like I had plenty of headroom. The manual lists the output as 1 full watt RMS into 32 ohms, so most of these low impedance planar models should do well (except of course the HE-6). Output rapidly diminishes into higher impedance loads, but I was able to drive my HD800 well enough. Yulong also suggests driving balanced headphones straight from the rear XLR outputs. I will try that when I get a chance. That's a similar scheme as his TubeDAC-11 made for Grant Fidelity (but that used RCA and an adapter to 1/4" headphone jack, rather than XLR). Not sure what the output impedance is on the XLRs - Yulong calls it "low impedance" but nothing more specific. Should probably be fine for 300 ohm HD800s though.
*The display is super nice. This probably won't apply on a silver model, but for my black unit: when the display gets dim it almost blends in with the enclosure. The black background of the display is deep enough to look like the black enclosure, and the text on the screen looks similar to the text next to the buttons for selecting source, filter, etc. It's very well done, and makes the otherwise nice Yulong D100 look absolutely primitive in comparison.
*The unit mutes output for a short time when you make a change in selection such as a new filter or changing the jitter eliminator. I assume this is to avoid a "pop" coming through during the change. Other DACs do that to some degree while selecting filters, and it's kind of annoying.
*Sound is pretty damn good so far. I only listened in pure DAC mode, single ended output to my Stax SRA-12S and SR-007. Great detail retrieval but still very well controlled and not harsh at all. I can't really say much more than that, still getting to know it.