This may seem like a stupid question, and thats likely because it is, but what is turning on “Blender GLSL Materials” suposed to do exactly?
All it does in most of my scenes is makes the faces of what i’m working with ever so slightly darker.
In some scenes it applies everythings vertex paint color without me asking it to, resulting in a sea of white.

In realtime CG you have two ways to calculate the light behavior in 3d models: per vertex ( old method ) or per pixel ( shaders )
When you set On the GLSL mode, you´re saying that you want use Shaders to render the materials. GLSL is the Shader language of OpenGL.
To work correctly with GLSL materials see the Blender Documentation about this here
Remember that not all VGAs work with GLSL and if your do it, make sure the drivers are updated.

Um… whats a VGA?