MahApps/MahApps.Metro — pull request #328 by punker76 (2013-01-27 20:36:39+00:00)
Title: Add property to add custom visual styles to TransitioningContentControl

try to fix this issue:

"This is still a ‘work in progress’ control, so there are some limitations - at the moment you can’t provide a custom transition without overriding the style of the control."