It looks like the Atlas December CTP is available for download. Nikhil Kothari already gave a quick tour of this new CTP.
The first few things you will notice is that most of the previously available controls, such as ListView, are no longer there (server-side). Instead, you can now use regular ASP.NET controls inside an UpdatePanel (see Nikhil's quick tour for more information on this subject). This should mean that there's no longer this duplication of controls (read: Atlas now seems to properly integrate with ASP.NET). As a result, it should be a lot easier to take an existing application and start using Atlas to replace postbacks with 'AJAX' requests.
While I'm glad they decided to go down this path, I wonder what will happen with the previously introduced concepts such as bindings. Can we expect to see them again (server-side) in a future release?
Another thing I noticed is that there is now a debug and release version of the script files. This makes it a lot easier to actually read the javascript and understand what is going on. Atlas will reference either the debug of release version of the script files based on the debug flag in the web.config.
I have updated the Atlas Class Browser. It now references the debug files of the December CTP.