Land use residential is difficult to derive automatically: and is in many ways more useful than lots of building outlines - however attractive they look on a rendered map.

Residential landuse can be used to infer significant properties of ground-sealing, water run-off, local heat-island effects, and aspects of local ecology. When building outlines are also present these properties can be refined (so that different parameters can be used for densely built-up areas ). This sort of data may be very useful for local campaign or conservation groups who often want good quality accessible data, but don’t have the resources of the developers or other interest groups.

I have, recently, tried to create landcover maps based on OSM data which can be directly compared to similar ones prepared for the European Environment Agency, see http://sk53-osm.blogspot.com/2011/01/simulating-urban-atlas-using-osm.html. The availability of landuse data, and particularly residential landuse made this process pretty easy.