There is a Google Document in the works that summarizes hundreds of Evergreen features. It includes Koha features side-by-side so you can get a better sense of how the two compare. Most importantly, you will see how very full-featured both products are!
If you'd rather check out Evergreen Features for yourself, make sure of teh Community Demo Servers. Information about those can be found here: http://open-ils.org/dokuwiki/doku.php?id=community_servers#community_demo_servers.
Another way for quick intro is to watch this 5-minute screencast (version 1.6). But note, Evergreen made some very big changes since 1.6 so you'll need to look beyond this screencast to get the whole story.
To find out more about the community of users and developers involved with Evergreen, join the General Mailing list: http://libmail.georgialibraries.org/mailman/listinfo/open-ils-general.
The official project pages for Evergreen are at http://evergreen-ils.org/.