Hi Folks
I have been working on a project where the requirement was to make the front end slick and basically use ajax where appropriate. At the time the decision was made to use Anthem.Net as Atlas had some issues with UpdatePanels.
Anthem.Net is very easy to get going with and to add it to a project is very straightforward. It also comes with quite a few good examples of how you could implement it within your web app.
One tool I would recommend for seeing whats going on is Nikhil Kothari's Asp.Net Developer Helper Tool which you can use to monitor callbacks and see the request/responses.
http://www.nikhilk.net/ASPNETDevHelperTool.aspx
When the first full release is out of Atlas it would be nice to over but for the mean time Anthem.Net gets the thumbs up.