In my last job we ended up rewriting the complete ASP.NET stack (forms, controls, validation, postback handling, ajax library etc...) - the reason I was given was that the ASP.NET controls were not accessible enough, not were any of the third party controls that were assessed for the project.
Can anyone point me to good accessible ASP.NET controls that do ajax as well?
Failing that, how would you approach creating accessible, ajax enabled controls?