Excellent way for retrieving data using ajax and the new ADO.Net Data Services. Data can be retrieved using JavaScript calls asynchronously making use of the success and failure methods.
http://www.asp.net/learn/3.5-SP1/video-239.aspx
The expand keyword allows you to control if all objects are returned or just the objects you are looking for to increase performance.
VS 2008 supports JavaScript intellisense and debugging so its easy to troubleshoot.
The examples in the video are similar to the ones here
http://quickstarts.asp.net/previews/ajax/adoaccess/QueryDataServiceAndAJAX.aspx