Yes, incunabulum.de is now running with Plone 4.
As the database of this site dates back to the Plone 2.0.x, this required quite some preparatory work. But after some initial fiddling around everything worked out quite nicely, as can be seen in my upgrade notes. Also, the skin was updated to incorporate some changes required for plone 4 compatibility, see the svn repository
And now? Well, we have a current and up-to-date system where things like improved galleries (collective.prettyphoto for single galleries and collective.plonetruegallery for inline galleries, see the hidden features section) will actually work. We will see.