I haven't found a DVD Audio disc yet either. I have a Panny DVD changer that says it supports the DVD Audio format, so if I ever find one, I'll try it. Not likely though, I'm not a big music collector.
I put the empty AUDIO_TS folder on the disc just because of a few reports on other forums that some players fail to play DVD-R's without them. I personally have never had that happen, and it is very likely those reports were from people who made other screwups, but since it only adds a couple seconds to the authoring process, and no space... what can it hurt?