Looks like Microsoft is going to demo the REST API and Virtual Earth. Someone needs to stop by and get the details.

ESRI Announces new REST API for Interoperability at 2007 User Conference

With the release of 9.3, ESRI will provide an ArcGIS JavaScript library that extends the Microsoft Virtual Earth Software Development Kit. You can use the extended SDK to mashup content from any ArcGIS 9.3 Server via the REST API for ArcGIS Server with Virtual Earth maps and imagery. In the Microsoft booth #2101 on the ESRI UC exhibition floor this week, the Virtual Earth team will be demonstrating this capability through 3 simple demos provided by the ESRI team.