They've just released ASP.NET Ajax (formerly ASP.NET "Atlas") in Beta 2 over on the ASP.NET site. (In fact, atlas.asp.net now redirects to ajax.asp.net.)
They've changed the control namespaces from atlas: to asp:, so I need to do a bit of search-'n'-replace on Mosaic Art by Siofra, my long-suffering "Atlas" demo, in order to port it into Beta 2.
I was just in Brad Abrams' presentation on the designer/developer workflow using Expression Web Designer (currently available for download in Beta 1 form) and Visual Studio Web Developer Express (a free download). I was impressed by some of the new designer functionality in Expression. A great toolset is coming together for ASP.NET web application builders!