The January CTP build of Atlas was made available today and can be downloaded from http://atlas.asp.net. This is a pretty big release of Atlas that has a number of new and improved goodies (I'm planning on hopefully doing some blog posts walking through some samples soon).
In particular, the Atlas team has spent a lot of time enhancing and fleshing out a number of the core scenarios around the new <atlas:updatepanel> server control -- including adding progress message support, error handling, support for Response.Redirects, and the ability to have some controls on a page perform regular full-page post-backs while others cause incremental Ajax updates of content.
Nikhil posted a great blog entry today that summarizes all of the additional features and enhancements to the <atlas:updatepanel> scenarios that were added as part of this new Atlas CTP drop. As you can see, there is now much richer support for error handling and updateprogress UI you can take advantage of as well.
Hope this helps,
P.S. You might have noticed the irony that the January CTP drop is being made available for download today (February 8th). It does take a little while to get the bits signed and propped onto the download servers, which is why the naming might at first seem a little odd. ;-)