lol no i dont use CSG hollow at all, and i don't use substract much either, mainly when i have some weird angled side to add to a brush, and when i do that i move the brush i want to modify far from every other thing around.
Actually I mostly use CSG to merge brushes.
Imho it gives lots more manoeuvrability when moving and manipulating brushes when u have far less. Besides, I'm not sure whether the brush count interfer in the compile time or not, i guess at least it has an influence on the .map size, thus on the loading time in radiant and the laggyness when working on ur map. I like to keep my brush count low.
Btw OldLady, the "Map Leaked" problem has nothing to do with CSG :)