Issue #3: Is ARIA supported?
• Screen readers
• ZoomText 9+
• JAWS 7.1+
• NVDA (free!)
• VoiceOver (free!)
• FireVox (free!)
• Orca
• JavaScript Libraries
• Jquery UI
• YUI
• Dojo
• ExtJS
• GWT
• Glow (BBC)
Screen readers. ZoomText 9+, JAWS 7.1+, NVDA, VoiceOver, FireVox, Orca. All differ, none are perfect.

JavaScript libraries: Many popular libraries (JQuery UI, YUI, Dojo, ExtJS, GWT) )are in the process of adding support for ARIA. Great resource is http://www.paciellogroup.com/blog/?p=313.