Here is a Revit -> 3dsmax -> Unity project that we worked on earlier this year.
the videos below are captured in HD in unity directly from some premade itween paths
Basic workflow was to export out the WorkSets from Revit as individual FBX files
Import them into 3dsmax with the file link manager, usually set to combine objects by material
from there run a set of scripts that collapsed / welded / AutoSmoothed / split meshes that were too large (65k verts is a pain) cleans up the layers, replaces materials, and exports the now unity friendly layers into different FBX’s for unitys consumption
Inside unity there are a few small steps needed, done mostly with AssetPostProcessors that hook up any external lightmaps that we generated in max, replace/reconnect any materials that are in our standard material library, and attach any components that are supplied in the max user properties fields.
bake the lighting to suit, (In this case, just give us some AO and Sunlight since we needed to be able to turn around revit design changes -> working webplayer overnight with minimal user babysitting.)
this workflow allowed the building owner to ‘walk’ around the design very rapidly after it was changed.
There are a few more captures up at http://vimeo.com/vsai/videos/ for anyone interested.