Since updating to beta-793 on Xperia XZ running Oreo, I've had a number of significant issues, and noticed a couple of points for improvement. I received the update yesterday, during an extremely stressful period for me, so my feedback via the app store may be less than subtle. For that I apologise, here is my more level headed feedback.
1) Widget barely functions
Widget populates well at first. But if Poweramp has been closed, the buttons do nothing 90% of the time. Only when Poweramp is already running do the buttons function. The widget will then often disappear, leaving only the buttons barely visible, and completely functionless (touching on them touches the desktop, as if they are not actually present but are still rendered). On top of the that, the buttons on the 5x1 widget overlap the edges of the widget and do not fit. Whether this is a conflict with Apex Launcher, I do not know.
2) music randomly pauses.
3) playlist wiping
I had a playlist that had been created originally when I first installed winamp. I maintained it for years, adding songs to it, but it was always my first playlist that had got me through multiple family deaths, serious life events etc. Yesterday, while listening to said playlist, I went to browse to another playlist, when, as I was scrolling my list of playlists, the "Chosen Slabs" playlist that I've been reffered to literally vanished from the list. It just blinked out of existence as I scrolled. I thought it must be a bug, so I rescanned multiple times - no playlist. I then checked the memory card files, and the playlist is still there - it's just now empty, sitting at 0kb. Years of work, of my favourite songs compiled into a single work, gone. I'm still totally confused as to how and why this occured.
4) you can no longer shuffle by playlist, only song and category. This is sorely missed functionality.
5) widget by default has the background invisible and no album artwork, buttons on a very low visibility.
6) pressing back from the player UI should take you back into the playlist you selected the song from, not to the top layer of the library.
7) list entries need to be visually smaller to allow more options on screen - as it is, choosing between list and list small only gives you 3-4 extra songs on screen. You cannot view an album this way without scrolling.
That's my pretty poor experience so far. As stated, running Sony Xperia XZ on OREO, using Apex launcher.