I thought I'd chime in quickly here as well. I've had the LD Dac for a couple of months now, running it mostly at work with a LD MKV amp, HD650's with blue dragon cable and (on occasion) my unmodified AKG 701's. I also have a Benchmark DAC1 which I run as the source in my hi-fi system, and for occasional late night headphone use.
I haven't done any detailed head-to-head comparison of the two setups, though I've been tempted to do so. There does seem to be a lack of information on the LD dac, and while I was comfortable taking the leap based on price, topology and previous happy experiences with LD, others seem to be gunshy.
What I can say based on general impressions is that the LD Dac + MKV is at the very least competitive with my 2008 Benchmark as a headphone rig, and at lower cost. The sound is very smooth and beguiling, while retaining fabulous detail to my ears. Without doing an A/B comparison, my sense is that the LD dac is distinctly warmer than the Benchmark (while I suppose some of this could be related to the different amp, I never thought the ss MKV ever felt particularly warm before now). Of course, I feel that the overall system synergy between the HD650, blue moon, MKV and LD dac is excellent and this might be giving it an unfair advantage. Then again, the dac alone could just be a better solution than the Benchmark (for me anyway, YMMV)...
If people are interested, I could try to write up a real review and comparison between the dacs. I'd try running both of the dacs off of SPDIF into the MKV to remove the amplification advantage (or so it seems to me) that my LD rig has at the moment. I'm also curious about SPDIF vs. USB on the two, though I don't have the USB version of the Benchmark (unfortunately). Alternately, potential buyers could just rest assured that the dac (and especially the MKV+Dac+HD650 pairing) sounds wonderful to these ears and represents a whole lot of audio nirvana for the money.