Kun engelsk ...
Jeremy then went through some basic demos showing how simple it is to fire up a map viewer app. First just an ArcGIS Online based app, then a Mash with Virtual earth and lastly with Google Map.
Communication is HTTP, SOAP or REST. The REST capabilities a certain ArcGIS server presents is based on the services directory (I might be mistaken here but that was what JB said).
The Javasvript API has a powerful eventing model making the basis for a rich client side design. This client has a map, a slider, navigation arrows and graphic layers. Some tools are available: Query, Identity and Search.
Key here is the access to Geoprocessing models on the server. Reason this is important that this is what makes ESRIs version so powerful. Neither Microsoft or Google has a geographic spatially enhanced back end.
Especially the Google version was interesting because of the access to Google Mapplets - small widgets within GM.
Right now the js api is for pushing data out NOT to recieve. If you draw something in the client you yourslef will have to handle teh JSON code coming back. But it will probably come in future releases.