The mighty IMAGTP armed with the Crysis (CryEngine2) are at the vanguard of using these real-time game engines for architecture and design visualisation. These guys pop up in any search for crysis and architecture and are an inspiration for the blending of these fields. The following 2 vids show off some of their work (both tests using the engine and finished visual projects).
[youtube vids of IMAGTP unleashing the CryEngine2 on design projects]
Diving into Crysis editing is something I am really keen to do, I just find myself helping out on a course using Unreal3 and doing all manner of other things of course.
For the Unreal 3 fans - dont forget to check out their Make Something Unreal Contest. There is an education category which could be interesting, but realistically this is for serious players with some serious time...