Via Christopher Steen:
Recently Bertrand posted OpenAjax InteropFest 1.0: Microsoft's entry. The OpenAjax's InteropFest's goal is to demonstrate how different Ajax libraries can be parts of the OpenAjax ecosystem and interact with each other through the OpenAjax hub.
Read all the details, including sample code in Bertand's blog post..
Good news for folks who don't want to have to choose just one AJAX library.