As usual ian hickon is being disingenuous when he says that the spec still has headers. Indeed it does, but in a neutered form that does not provide the ability to mark up complex tables such that current AT will be able to decipher the relationships between header and data cells. As for the alt attribute, while it may be documented in much more detail than HTML, much of the documentation is of poor quality and in conflict with WCAG 1.0 and WCAG 2.0.

Both of these issues are being reviewed by the W3C protocols and formats working group, who has expertise and knowledge in regards to accessibility and is responsible for ensuring accessibility considerations are taken into account in all specifications produced within the W3C. So we don't have to rely upon only one persons view of what is good for people with disabilities.