Just wanted to add that I picked this unit up based on this review, and after a month of ownership I couldn't be happier. The unit is absolutely dead silent and only warm to the touch after being on continuously. It also remembers the input source when powered on/off which is a nice touch over previous models. My only request would be for a front panel power switch and pre-amp section. It'd also be nice if the unit could stack with the Yulong Amp one as the prior units did :0
I did have one issue with my unit and that was with using the USB inputs. I found that while switching between full screen apps (for example video games), the D100 would lose signal lock and put out a very loud, nasty hiss. This seemed to only be a problem with my Gigabyte USB 3.0 board. Going back to a USB 2.0 board on my wife's computer turned out to eliminate the problem. Using optical output also fixes the problem.
Sonically, I think the DAC section compares very well to the Stello DA100 which it is replacing. I honestly can't tell much of a difference with most music (or between the usb and digital inputs), and I think you'd need to be intimately familiar with both the program material and source to be able to differentiate the two. Compared to the soundcard analog out there's a subtle (as in only an audiophile would notice), but noticeable difference in overall space, smoothness, and top end clarity. In all honesty I think you couldn't ask for more in a DAC and I wouldn't spend more money for the improvements I've heard in megabuck DACs. That money would probably be better spent upgrading your headphones or amps.
While the amp section is very nice if you're on a budget, it does lack control as volume increases.... although at that point I'm unsure if its my headphones (hd600) that are giving out or the amp. I don't have anything to compare it to other than my dv337 and it doesn't really compare, although again the differences are subtle unless you are very familiar with both amps and the program material. I just felt the dv337 had a touch less grain, a little more space, and stronger/more controlled bass.
Very happy overall with the value and performance as a DAC only, and if you were to use the headphone amp I think you would have an unbeatable combo for the money.