The RC for Microsoft AJAX went up on the ajax.asp.net site today. The release of what was originally code-named Atlas is now imminent. I like to joke that I'm an AJAX expert because I have been using the UpdatePanel for those magical partial postbacks. There is so much more to AJAX, whether you are using the core part of it - ASP.NET AJAX - or adding in the AJAX Control Toolkit (a slew of opensource controls developed via CodePlex) or the AJAX Library which enables developers to create controls.
This has been an amazing effort by the ASP.NET team and it's great to see them closing in on the release.
If you have been working with earlier pre-release versions of AJAX, definitely check out the ReadMe file for some last minute breaking changes - most importantly as they wrap the namespace into the core .NET Framework, it becomes System.Web.xxxxx rather than Microsoft.Web.xxxxx.