Good news and not so good news...
I was in my local Best Buy this morning. Saw they had 1 of the new AFTV HDR's. Grabbed it!
During lunch. I set it up.
I have a Denon X2200W that I plug all my devices into - an NVidia Shield TV and Roku Ultra and now the AFTV HDR.
The Denon feeds a Samsung UN65JS8500 4K UHD TV that supports HDR.
I had a Fire TV 4K in the same chain and moved that to my basement TV. I plugged the new AFTV HDR into the same HDMI input as the orginal AFTV
Ok, started it up, let it update, signed in and off the the races.
First, under Settings -> Display and Sound there are some new setttings. I left the resolution to 4K Auto (I am hoping/assuming this implies auto frame rate switching). Under Depth there is 8 bit, 10 bit and 12 bit. 8 was the default so I changed it to 10 bit. Under Color Space it lets to select RGB (default) or YCbCr. I selected YCbCr.
First test - started Netflix and started to watch a movie that had the HDR badge. The AFTV HDR went into HDR mode (as did the TV) and it played the movie. Looked ok.
Stopped playing and exited Netflix.... HDR still ON!!!
Home screen is all blown out. So, went back into Netflix and tried playing a non HDR 4K movie. HDR stayed on...
Exited Netflix - HDR still on - home screen blown out.
Reset AFTV HDR - all back to normal.
This time went into Amazon Video. Played Grand Tour. HDR mode goes on and Grand Tour looks great.
Stop playing video and exit to home screen.
HDR still on.... home screen and images are all blown out, over saturated...
Went back into Amazon Video and tried a non-HDR movie. HDR still enabled - move is not looking good ;-)
Reset AFTV HDR - back to normal.
Last experiment - Go into Amazon Video - play Grand Tour. HDR kicks in, looks good. Exit video and HDR still enabled.
This time, I changed the input on the Denon AVR from the AFTV HDR to any other input (in this case the Roku). Then, went back and selected the input the AFTV HDR is plugged into.
Interesting, HDR is now off and everything is back to normal.
As a side, the NVidia Shield is a good example of switching back and forth correctly. The Netflix app only switches into HDR mode when the source is HDR and exits as soon as you exit the movie. Kodi/SPMC (on the NVidia Shield) also handle gracefully going in and out of HDR mode when appropriate.
So, long story short - if you get one the next few days keep an eye out on the AFTV HDR getting stuck in HDR mode when it shouldn't. If it gets stuck you will either need to reset the box or try switching HDMI inputs - maybe the HDMI handshake gets things back to normal.
I would think a software update with clear this issue up.