Tyrann: Could you add to your Qbsp support for floating point rotations of textures (so for instance, rotating a texture 22.5 degrees doesn't get rounded to 22 degrees)? Frib (or I guess a friend of his) added it to Bengt's modification of TreeQbsp, but it'd be nice to have with your func_details!
Some test shots, showing exactly what Tyrann just explained...
http://i.imgur.com/NHpU9eH.jpg
Here, the red textured brushes are func_detail brushes, and we can see that they still cut into the hull of the world. (the crate in the middle of the screen is a floating cube, world geometry)
http://i.imgur.com/LpQbmQU.jpg
Here you can see that that the PVS does not consider the func_detail brushes, as the floating crate cube is still rendered.
http://i.imgur.com/ajkNDg0.jpg
Here is that same view, except the red textured brushes are normal geometry, to prove that the crate would normally not be rendered in this location.
These detail brushes are good for speeding up your Vis time by simplifying the PVS. They are NOT for reducing r_speeds.