w3c - Scope attribute in Table tag

Yes, I'm just full of questions this week.  Thanks to everyone for the info on requirements/procedures.

Next question:  I'm attempting to figure out the proper method of tagging for tables.  In the past I had used <th> and <td> with "header" and "id" as per W3C.  However, the 508 requirements from the Access Board say to just use the scope attribute.  What do you all think?  Which is better for data tables? and layout tables?  Which readers pick up the scope tag?  

As always, thanks!
Brooke Dine
Information Specialist
National Center for Biotechnology Information (NCBI)
National Library of Medicine/NIH
Bethesda, MD 20892