I know a9 didn't work for many people, but I’ve been using it for quite some time now. I'm about to go back to a8. But I figured I’d post this first.

In the car, my player always seems to lockup after a playlist ends. The UI will still function, well mostly. The track title usually always is locked on the last track in the playlist, but the play/pause icon toggles on top button press. The TrackNumber area does update on left/right presses, but the Title remains frozen with no audio output.
I'll hold the top button down to get into standby, then remove and insert back into the cage.

Another thing is it seems, in the car, the drives are always spun up, even with the latest HiJack. The Disk Icon is the gray background one with 3 dots on the right of it.

I also didn't loose a single playlist on upgrade from 2.0 -> a9

I also haven't been using the player at all on AC recently so I’m not sure if these bugs are present on AC.