Megaton Cat, you are right about full map design. First, lay out the shape of the map with brushes. Then go through and fill in details with meshes. This will make it much easier to design each area, because you know where the map goes, and it already has flow.
I am designing this map as a symmatrical CTF-type map. I am going to design 1/4 of it, and then just copy and mirror it four times. Because I first created the shape of the map with brushes, I was able to design all this in a couple of hours.
The rooms are divided up into visgroups, so I can show and hide them if I just want to work on one area.
Here's one of the meshes I designed for it. It would be silly to try to design something this complex with brushes. I just model it once in max, and create an instance of the mesh anywhere I need it. If I decide I want to change the mesh a little bit, I can overwrite the old one, and the map will just load the updated mesh.
WindowsXP Media Center Edition, Pentium 4 2.53 GHz CPU, 512 MB of RAM, GEForce4 MX 440