This is a very short blog, but it appears that the GlobalNavigationNodes member on the PublishingWeb class has moved in SharePoint 2010.
In SharePoint 2007, this was under Microsoft.SharePoint.Publishing.PublishingWeb.GlobalNavigationNodes
In SP2010, this has moved under Microsoft.SharePoint.Publishing.PublishingWeb.Navigation.PortalNavigation.GlobalNavigationNodes
This particular property is used to read a publishing site's navigation settings - I've used this to export site navigation as XML to accompany a site export. Since site exports doesn't seem to include any customized site navigation information. (It still doesn't in SP2010).