Got my shipment today, too. I've listened for an hour or two, and I'm not happy at all. While the DAC probably isn't bad at all, this thing is NOT an amp. It can't even drive a very easy pair of over-the-ears to an acceptable volume level. So I don't care how good the DAC is if I have to put it through an amp. I have other combo units (bigger) that I can use instead, the major draw of this was the size.
YMMV, but I didn't need to use the app (which is awful and I've had to reinstall twice already) to listen to normal iTunes music. I have other apps that can do FLAC, I'll give them a try tomorrow to see how they sound. The only thing I'd use the app for is upgrading the Firmware.