I've heard some good ESS9018 implementations and the Concero falls slightly short in that regard when it comes to ultimate detail retrieval though more detailed than some Wolfson DACs I've listened to (Rega DAC, Emotiva XDA-2, Rotel RCD-12). Still a cracker at the price and easily belongs in the class of the Audiolab M-DAC, Rega DAC, Schiit Bifrost and PS Audio NuWave. I haven't heard the Bifrost (might soon) but I still like the Concero more than those DACs I have listed and have listening experience with. I have also owned mine for around 1,5 years now and I'll probably never sell it.
Its a well balanced DAC from top to bottom, good sound staging and its has plenty of versatility built into it. The only thing I could wish for was slightly more bass extension and bit more body to instruments and the 1.2Vrms makes DAC level matched comparisons tricky. Lots of mainstream DACs have some issues in the treble and this one handily walks around that. It's also a terrific USB->SPDIF converter just slightly behind the AP2 I have as well..