Very interesting news via the Arch Network: A group of award-winning architect/design studios called Hometta are about to launch "H-Town," a virtual world showcase of their real world building designs. It's been developed in OpenSim, and unless I'm mistaken, it's the most prominent real world commercial application of Second Life's open source spinoff so far. (At least in the West.) Not just a platform for 3D model displays, H-Town will also let prospective Hometta clients experiment with different paint, furniture, and landscape choices. Much more here.
Update, 3/30: Just received some more details from Hometta's Ann Chou:
Hamlet Au: What inspired you guys to use OpenSim? Why not Second Life?
AC: While we currently use OpenSim, we may expand in the future. The purpose of our virtual world, H-Town, is to give our customers an additional tool in visualizing their prospective home. Although Second Life and OpenSim have a lot of similarities, there are several reasons why we chose OpenSim over SecondLife. We intend for H-Town to create a design community, whereas a real estate market has already been developed in Second Life. In order to build this kind of development project, we have to invest quite a bit to acquire several lots. Under OpenSim, the basic [SL] rate could provide four sims.
In order to simulate the real houses, the houses in H-Town must attain a certain level of detail. In Second Life, we have a prim limit of 117 prims in 512 m2, as well as the texture uploaded fee.
OpenSim seems more appropriate for H-Town's purpose, as it allows to develop a private community. Of course, Second Life has a lot of traffic. We see Second Life as a potential outlet for Hometta in the future.