As promised, Berlin is today available in 3D, as a downloadable network link. A pleasant surprise — a good portion of the buildings are textured!
Of course there is a caveat: Everybody wants to check this out, so the servers are overloaded, and you will likely not get to actually see buildings for the next day. So, while waiting for the network link to work, enjoy some screenshots on the official site.
(Note: I am sure that the fact Berlin got this done before Hamburg has nothing to do with inter-city rivalry:-)
(Thanks to Frank via the comments)
[Update 15:31 UTC: The current implementation, bizarrely, is not Mac compatible.]