Several enhancements have been added to ASP.NET with the release of Beta versions of Visual Studio 2008 SP1 and .NET 3.5 SP1...

One of the good enhancements has to be the Script Combination ability where you will be able to select the number of scripts you need to in your page to AJAX enable it and improve the performance of it...

Check out this video at www.asp.net

http://www.asp.net/learn/3.5-extensions-videos/video-296.aspx