Thank you both. I actually sent an e-mail to GW microtech (window eyes) and I got this answer from them:
Screen readers don't support aural stylesheets. One of the biggest reasons is because it takes speech control away from the speech user, which is akin to having someone turn a sighted person's monitor upside down, and invert the colors, without asking permission. In addition, there has been no user demand for aural stylesheet support, so we simply haven't invested the resources into supporting them.
As for my second question, I just wanted to know if media="aural, speech" would break in the future because the 'aural' keyword will become deprecated. But it seems the question is academic.
But this information raises another question which I will post in a new thread [webmasterworld.com].
(I am also wondering why W3C puts so much effort in aural/speech development if there is no demand for it?)
[edited by: Bert36 at 2:23 pm (utc) on Aug. 2, 2007]