This release provides a great stabilization of the Flamingo Skin, and includes new themes and some improvements to manage them.
It also contains a new mail API and module to replace the old mailsender plugin, a new dynamic tree widget that is progressively replacing all existing trees in XWiki (Document Index, Navigation Panels, etc...), some improvements on the Extension Manager as well as on the User Directory and the Applications Panel.
Efforts have been made on the performances side, with good results on view mode (except on the first loaded-page). We reach the same performances as 5.4.6, which was not the case during the 6.x cycle until now. This is a first milestone to get even better!
Finally, and like every releases, a lot of bugs have been fixed.
Full release notes available at http://www.xwiki.org/xwiki/bin/view/ReleaseNotes/ReleaseNotesXWiki63