OpenDocument v1.1 includes a number of specific improvements for accessibility, including:

• Alternative text for non-text objects 
  
• Proper association of captions to captioned content
• Encoding of pagination information
• Preservation of table semantic structure imported from other file formats
• Proper encoding of authored table header content
• Author-defined logical navigation of page objects in presentations
• Provision of alternative text hints for hyperlinks

It's important to note that many of the concerns around accessibility for people with disabilities have to do with the accessibility of the applications that implement the OpenDocument format.  This includes questions about the built-in features of OpenDocument applications that meet the needs of people with disabilities, and questions about how well OpenDocument applications work with specialized assistive technology applications used by people with more severe disabilities.