The gang at Digital Urban are one of our idols in the use of interesting technologies and their data sets. They are always experimenting with various real-time game engines and Unity is no exception. The Digital Urban blog sites Unity3D as their "development platform of choice" and their experiments are interesting as always.
Here are some bits from their efforts:
[Image from the Digital Urban blog of a Unity3D project]
There are others of course who are looking at the engine for visualisation projects of various types. Here are some links to more:
Chez Keystone's house in Unity starting with his Revit model on The Arch Network: LINK
RHDs exhibition visualisation - direct to the Unity player : LINK
Thread on Arch Viz on the Unity Forums (more links to follow): LINK