I've joined the Concero club, having received the bundle with Apple Remote yesterday, purchased used, but it's very much in mint condition. :-)
Well, after no more than four hours of listening, yesterday evening and this morning, I'm an idiot for saying this so prematurely - but I can't help myself - switching as quickly as I can between my DACmini CX DAC and the Concero, expectation bias has pretty much been ruled out: The DACmini CX gets clobbered by the Concero in really busy, congested, recordings, when it comes to separation of instruments.
With tracks having wall-of-sound busy-ness, such as Daft Punk's Tron Legacy (End Titles), the DACmini CX can't compete. I'm hearing spectacular de-congestion / unscrambling of that track with the Concero (with or without up-sampling). And for several jazz recordings, brushes on cymbals are killer with the Concero - freaking amazing micro-detail and a very natural sound.
I had held off on getting the Concero for a long time, because I've got considerable experience with some much less expensive implementations of the ESS9023 that were disappointing (including the Stoner Accoustics UD100, the JDS Labs ODAC, and the Audioquest Dragonfly - which was far better than the first two, but I still didn't care for its tendency to sound glaring in the treble). For the record, I don't like the dark or "musical" sound of WMxxxx or PCMxxxx DACs, at least not with my LCD-2, which by itself has all the warmth and coloration I want, when used with a neutral and transparent amp, but my earlier experiences with the ESS9023 were just too "shiny" for my tastes.
Not so the Concero's implementation of the ESS9023. If ever there were an example of how the implementation of a DAC chip can make all the difference, this is it. To my ESS9023-tainted ears, the Concero doesn't sound like its using an ESS9023. The treble is so clean and transparent, completely without any annoyances whatsoever. And it has none of the very slight "etch" of the DACmini CX DAC section. Just grainless, natural-sounding detail. I realize this isn't saying much, given my lack of exposure to the killer expensive DACs, but for now, the Concero is the best DAC I've ever heard - by quite a margin.
More: Even though I can say that the two up-sampling filters sound "different" from running without any up-sampling, I still can't put my finger on how to describe that difference and I can't tell any difference at all between IIR and Apodizing - not yet, anyway. In short, at this early point in the game, I'd say I could live without up-sampling, but I'll keep looking for differences. (I do have my "Speaker Properties > Advanced tab" set to 24-bit/192000 Hz, in Windows 7 - to support the 4x up-sampling of 44.1 files.)
Also: I was pleasantly surprised to find that the Apple Remote actually works with Foobar 2000 - to select the next or previous track, and to pause or play. I really didn't expect Foobar to be compatible with that feature of the Concero!
Here are my chains, for the sake of putting my comments into context:
44.1/16 and 96/24 WAV on SD cards > Windows 7 laptop > Foobar 2000 w/WASAPI event mode > Concero's USB driver > Moon Audio Blue Dragon USB cable > Resonessence Labs Concero > Emotiva RCA Interconnects > 24VDC LiPo battery-powered TBI Audio Millenia MG3 amp (32Wpc into 8-Ohms) > TBI-built impedance match > 50-Ohm LCD-2 rev.1
or... take out the impedance match and the LCD-2 to go to a pair of Definitive Technology SM45 near-field monitors (90 dB sensitivity).
Very pleased with the Concero,