Access improvements to Windows 8 include:
Redesigned Narrator to improve its performance so that it quickly reads out what you have selected.
Added more languages and voices to Narrator to support additional countries and preferences.
Updated components and features within Windows to leverage UI Automation that allows them to be read by Narrator.
Updated UI Automation (UIA) with more text patterns and document content so that Narrator can use it to read the outputs from applications.
Read more on the Building Windows 8 Blog.