Used a few times. No operational problems. Comparing it to the Fiio BTR11, which I also own: The sound quality is about the same when using AAC connection. The battery life is also better on this one. With 4-pole earphones with a microphone, the earphone's microphone is enabled, so the microphone sound quality is better than the Fiio BTR11 (the Fiio BTR11 does not support earphone microphones). Even when using earphones without a microphone, the built-in microphones (two of them) provide noise cancellation, resulting in higher call quality than the Fiio BTR11 (which has one microphone). Thank you.