The quirks are
Output from rear channels when playing stereo, unless "Pure Audio" is selected
The display on the screen goes out unless you choose "Pure Audio"
Pure Audio, Pure Direct and the other audio selections have no effect when using USB audio. They only work on HDMI
There is no DSD support for HDMI audio, so you cannot play SACDs on a player having HDMI audio out
On the particular unit I have, I am unable to select any items on both GUI menus. Since this worked on another HD-AVP I borrowed, I hope the agent will exchange the unit I have
The user guide is not much use. It mentions the various choices, but does not explain what they do
Beware disabling inputs on the input setup menu, or assigning HDMI video to a co-ax input. When you do that, you cannot access USB from the remote, but need to to it with the manual selector on the front panel. If you undo your changes, then you can select USB by pressing Input and scrolling down to USB
Pressing the USB button on the remote brings up the Home Menu, not USB
Several buttons on the remote do nothing at all
After much complaining, I have realised that the only thing I am going to get fixed is the GUI menus. The lack of DSD on HDMI is irksome, had I known that beforehand I would not have purchased it
But if you are only going to use it for 2 channel listening, then I would recommend it. Just test everything thoroughly the first week, when you get used to how it operates