As far as LIO customers, brh posted this and made some comparisons to other dacs:
http://www.audiocircle.com/index.php?topic=132609.msg1405772#msg1405772
To expand a bit, having used LIO more extensively at this point - my main point of reference was the Concero HD, which is often described at punching above its price point, and which I think is sonically quite similar to LIO's DAC. I was very happy with this DAC, and had no real desire to spend big bucks upgrading. I was considering buying a second Concero before getting LIO, as my first one seemed like it just wasn't quite meant to be. But, of course, LIO came along, and the idea of tucking my DAC away inside a modular integrated was far more appealing, so I held off on replacing my ailing Concero. Now, to the point, it's hard to compare prices when LIO's DAC must be taken as a part of the system, but ignoring that, the LIO module is $695 vs. $850 for the Concero HD (which, again, is often described as sounding above that price point). To me, LIO's DAC sounds more detailed, more resolved, just... purer. I doubt anyone could claim it's not on par with the Concero HD, and I personally think it sounds decidedly better.
They do each have a few different tricks up their sleeves: Concero can be used as a USB to S/PDIF converter, which is nice; Concero's firmware is easily upgraded (not sure what the situation is re: firmware on LIO/the LIO DAC specifically... Vinnie?); Concero allows for digital attenuation via system volume control (I get why this isn't generally desirable, but for casual listening it
does come in handy). On the other hand, the DAC chips on LIO's module sit on a separate daughterboard, allowing for modularity atop modularity! Very cool, and I look forward to seeing what Vinnie does with this.