Using it for few weeks now. Apart from reporting some minor issues and fixing it with new FW updates - AP80 works good and smooth. Haven't got a single hiccup on latest 0.08 or 0.09 betas, everything is nice and fluid even after long drowsing though folders. apps, menus, etc. We had ~9 issues list initially, now, half of those are solved by Hidizs with 0.09FW. Even DSD128 playback is here.
Concerning the second part of your long post - you are trying to describe the ideal FW logics that would fit your expectations... Moreover, the main company in charge for such things is Hiby, not Hidizs. Hidizs utilizes their FW and submits found bugs similar to the way we submit it to Hidizs. Therefore, your expectations and ideal logics should be initially directed to Hiby company.
Multiple ways of adjusting sound - I like it. No more swipe down. Only swipe up and everything is combined there now.
Swipe to change backlight - why not instead of going to system menu and changing it there?
Many people -> many perceptions -> many expectations.