I've used on-board audio a few times, but it's rough. The only case that comes to mind where it was really successful IMO is if you're using an FPV quad to cha

I've used on-board audio a few times, but it's rough. The only case that comes to mind where it was really successful IMO is if you're using an FPV quad to chase a vehicle: race cars, dirt bikes, monster trucks, etc. All of those things are loud enough that they're clearly audible over the prop and wind noise. If anything, for dynamic chase footage, the sound of the quad's motors spinning up adds interest. Otherwise, you're not going to hear anything worthwhile from the air.