If you want to check out what a real-world complex Atlas application would look like, Nikhil put together an amazing Atlas app around Virtual Earth and a few other web services such as Flickr and Amazon.
Not only is this application technically impressive (check out the source code: the page is purely declarative, using only XHTML and XML-script markup), it's also nicely designed and has the classical "Nikhil touch" that you know if you read his blog. Of course it still has a few rough edges like Firefox compatibility and performance but still it's impressive to see what can be done with pre-alpha technology like Atlas.
It's amusing to note that like anything great, it attracts some pretty stupid comment, like this one: "If it's not web standards, it does not belong on the web. Please take that down."
The Virtual Places blog post: http://www.nikhilk.net/VirtualPlaces.aspx
The Virtual Places page: http://apps.nikhilk.net/VirtualPlaces/