Web development will be much smoother now specially if you are JavaScript, JQuery, or AJAX lover.
Intellisense for JavaScript
Now you don't have to think and type your JavaScript objects. Intellisense support in Visual Studio 2010 will help you listing objects and related code.
Integration of JQuery Framework
Today, JQuery perhaps is the hottest technology in Web development and Microsoft and Visual Studio team had realized this. That is why they have added JQuery support (of course with Intellisense) to Visual Studio 2010. How cool is that? Well done!
Better and improved AJAX Framework
AJAX and dynamic page creation process has improved in Visual Studio 2010 that will benefit Web developers who use AJAX in their applications.
Multiple monitor support for coding and debugging.
Improved Sharepoint development with new templates.