This is the second release of the 4.x cycle. This release brings Extension Manager improvements such as merging of configuration documents during extension upgrade, a more gentle learning curve by hiding internal documents from non-technical users, and lots of goodies for the developers such as easy sharing of variables between scripts in different languages.

See: http://www.xwiki.org/xwiki/bin/view/ReleaseNotes/ReleaseNotesXWikiEnterprise41