ASP.NET AJAX has split into separate "core" and "additional" features for the 1.0 release. The "core" features will become a fully supported Microsoft product at v1.0 (ie you can get support from Product Support Services, they follow MS standard support lifecycle etc). The "additional" features are an optional download that bridge the gap between the "core" feature set and the features that you've become used to in the CTPs to date. For more details see the feature matrix ("Feature Matrix" tab) and Scott Guthrie's original blog post " Atlas" 1.0 Naming and Roadmap ".
There is a comprehensive whitepaper describing the changes between CTP and v1.0 Beta releases and also a migration guide for those of you who've built ASP.NET AJAX sites with the CTPs . Documentation has also been updated. As has the Control Toolkit .