I generally use Poweramp to play music (on "album shuffle") in my car as I drive, with Waze running. Poweramp plays through my car's bluetooth audio system, and I set Waze to use the phone's speaker for its audio prompts.
When I set Poweramp to "respect audio focus", every time Waze has something to say, Poweramp stops playing entirely; stopping and restarting the audio both seem to be slightly slow. This mode of operation can be extremely annoying, particularly when Waze gives a bunch of audio prompts in rapid succession. ("In 400 meters, at the roundabout, take the second exit. In 200 meters, at the roundabout, take the second exit. At the roundabout, take the second exit." Get the picture?) As a result, I've set "respect audio focus" off, and I have to hear the Waze prompts (some of which are actually important) over the full-volume music.
Another audio player I've used - which shall remain nameless, but has the initials "N7 Player" - implements "respect audio focus" by lowering the volume of the music playing over bluetooth, without actually stopping the music. This mode of operation is far less annoying, and I would love to see it implemented (either as the normal "respect audio focus" mode or as an option) in Poweramp. (I've got other problems with N7 Player, which prevent me from using it in my car.)
If this kind of "kinder, gentler" respect-audio-focus mode could be made available in Poweramp, I'd be most grateful!