One of the things that happened in Kestrel is that we have re-established support for screen readers. As of today (2008-04) it is still in development, but you can test it out in the weekly builds.
Currently it is enabled for Windows but windows screen readers don't seem to work well. It is also enabled for Macintosh OS X.4 and above, with the built-in VoiceOver? where it is not entirely terrible to use. It does support a fair bit of ARIA, and does something in OperaChat, mail, etc etc.
Feel free to give feedback to ChaalsMc ...