With the new firmware, it looks like the four biggest remaining items are: DTS-X Certification, PRIR from single speaker, vertical headtracking, and a web-based GUI.
I installed the new A16 firmware today, including updating the HT firmware, thus facilitating a new optical-only "legacy A8" mode of operation with the ST. Then I went through the regular steps following a full factory reset including turning off key pad solo keys, turning on preset-based SOURCE and increasing max volume above 79. I then re-entered my user name, rebuilt my two PCM listening rooms (5.1 and 7.1) from the preserved internal AIX PRIRs, as well as constructing my Atmos room (9.1.6) by first adding "all speakers" from the BBC PRIR, and then overlaying the 7.1 horizontal speakers from my AIX 7.1 PRIR. Finally, I recreated my presets 1-9 (5.1, 7.1 and 9.1.6, for each input HDMI1, HDMI2 and HDMI3) to include my preserved internal Stax SR-009 HPEQ. I think I may now have this procedure pretty much committed to memory. Next time it's necessary I may not even reference the manual.
Also, having never done it before now (although I was informed a while back that it was actually required), I also used this opportunity to perform the obligatory HT [re-]calibration process, first placing the HT in the freezer for 1/2 hour, etc. Sure enough it took about 20 minutes and the HT LED went through all of the predicted color changes and blinks, eventually setlling down to a solid green. While waiting for it to complete I did take the time to read the manual regarding the several ways the new A16 HT can now operate in.
So now I was pretty much ready to try things out with the new firmware. There was one very significant change in my setup environment however, in that I've recently replaced my old Panasonic 65VT50 (1080p) with a new 65" LG OLED C9 (4K). This is quite significant because the Panny plasma panel was relatively "thick", including the chrome bezel edging all around the glass. With the Panny there was a flat top edge around 1/2" thick of chrome that I could nicely affix the A16's ST to (using 2-sided tape). However the LG C9 pretty much has nothing but thin glass with a thin black metal edging all around it. So the LG's top edge and most of its visible area is actually only .1" thick (electronics contained in a thicker part down in the the bottom-back of the set), thus well deserving of its description of "picture on glass". Actually, the E9 model IS "picture on glass", with 100% of the panel being .1" thick (electronics in a separate unit connected by a ribbon cable to the panel). In any case it is now very problematic to attach the A16 ST to the top edge of my C9 which is only .1" thick. In fact at the moment the ST is NOT re-attached to the top edge of the TV and thus is also NOT re-connected to the A16.
This forced me to learn about and experiment with HT modes that do not involve use of the ST, namely "none" and "magnetic". So I also learned about the "+0 azimuth reset" button on top of the HT which is a terrific feature that allows you to watch TV from an "off-center" seat location or non-perpendicular off-angle from the TV (as would be required if you were using optical-only A8-mode) and yet still have the sound appear to be coming straight at you from L/R as if you were truly seated centrally and looking straight ahead at the screen.
Turns out "magnetic" works great for me! I never knew! No more ST green lights to distract, no more having to physically center myself directly opposite the ST and always look straight ahead in order to get balanced L/R sound in my ears. While obviously even using "magnetic" the sound field moves as I turn my head left or right (same as when using the ST and optical stabilization), it actually sounds very very natural to have this happen without involving the ST. Maybe it's the freedom to sit anywhere and look at the TV from any angle, and then "reset +0 azimuth" with the button so that now whatever is the "look angle" at the TV, that's balanced L/R sound seemingly "coming straight at you".
Excellent! I think I've found my HT mode of choice, and it is NOT "A8 legacy". Nor will it likely involve using the ST and optical stabilization. "Magnetic" FTW.
Now regarding other items presumably fixed in this latest firmware update, I can report that ALL OF MY CLICKS AND NOISES ARE GONE! No more minor noises during the power-on of the A16. No more minor noises during the initial loading of presets at the end of the power-on process.
And most impressive, NO MORE BIG POP WHEN CHANGING PRESET!
Interestlingly, I can still hear the big relay in my external DAC go OPEN right after I push a preset button on the A16 remote, at the start of the process when things are now apparently getting muted properly (by the fix in 1.80) on the optical output to the DAC. Then a few seconds later when the new preset has been fully loaded and all things internal properly initialized, things are apparently then getting un-muted properly and I can once again hear the big relay in my external DAC close, making real sound once again available to the headphones.
And throughout the entire process of changing to a new preset it has now been TOTAL SILENCE from the headphones. No more BIG POP. Of course through the open Stax phones I can easily hear the big physical OPEN and CLOSE sound of the relay in the DAC (unique to my Audio-GD NFB9 DAC for sure, but maybe in others as well, although not using the internal DAC in the A16). But thankfully the previously startling BIG POP from the headphones has been successfully disappeared due to the 1.80 firmware fix of this issue.