I'm not blaming Toast. I'm even more upset with Apple with this decision. All I meant to say was that I wish the Toast product description would state that it can't use iTunes songs to burn audio DVDs, because I would venture to bet that many people buy Toast for this function. Of course, stating this upfront may affect Toast sales.
For the difference between audio-DVDs and DVD-Audio discs, I understood the difference to be that an audio-DVD can have songs on it much like any audio-CD. On a DVD-Audio disc, the music is generally mixed specifically for the increased audio capability of DVD, like 5.1 surround. And, you need a DVD player or car system that can actually play a DVD-audio disc. Unless the player states that it will play DVD-Audio, it can't. This seems to be a unique audio format.