1. Basic type inference
3. IntelliSense from XML comments for functions, parameters and return types
4. Calling web services using ASP.NET AJAX
Additionally, VS2010 RTM had some improvement, including:
1. IntelliSense when manipulating browser objects
2. Dynamic generated variable IntelliSense
Scott Guthrie has a brief blog covering some of these.
1. Dynamically generated IntelliSense will override the XML commented return types.
For example, the following code snippet shows string IntelliSense, instead of number IntelliSense:
This may lead to a confusing result sometimes. The best way to solve this is to create a vsdoc commenting file, and remove the conflicting return statement from such functions, just like jquery-1.4.1-vsdoc.js in VS2010 RTM:
Some useful links:
Web Platform and Tools