The Button ARIA Plugin makes it easy to use the WAI-ARIA Roles and States with the Button and ButtonGroup controls. Using the ARIA plugin, Buttons are more interoperable with assistive technologies (AT), such as screen readers, making them more accessible to users with disabilities.
Watch a screen cast of this example running in Firefox 3 with the NVDA screen reader, to see immediately the benefits that ARIA provides, or download the latest development snapshot of NVDA to test this example for yourself.