Organic Groups and Workbench or Revisioning together. Will this work?
We've built a D7 site with Organic Groups and Revisioning and have found that installing Organic Groups causes a pretty major problem with Revisioning in that the Author and Moderator roles cannot see unpublished content.  We've confirmed on a clean Drupal installation that Organic Groups Access Control is the cause of the issue.

The only workaround that we found was to check the Bypass Access Control checkbox for those roles.  That means those roles bypass all security checks on content on the site so they can edit/delete/publish any content.  That is an okay work around for our site but did present a problem when we wanted a separate moderator role for just one content type.

See this post for full details -> http://drupal.org/node/1494232

We are planning on looking at Workbench for a different D7 site because Revisioning and Rules isn't going to be sufficient for the workflows.