Thanks for the nice comments.
Namespace Irrlightuser:
...(What a funny name!)
This scene renders with light-speed

But this is what I expected, since it is only one model plus a static shadow map (1024px, generated by IrrEdit).
These models have LOD-stages. The building above is lod stage 0 and there are 2 additional stages available with less polygons. You can see details here:
http://www.dexsoft-games.com/models/ima ... /index.pdf
If you have a possibility for good culling (like using occlusion culling geometry inside the houses) then you can render a complete city of them. If you are close to one house it will prevent rendering all other geometry behind it.
So it depends on the scene-management how many you can use in one scene.