To answer your question about why you'd want a shader for the texture box demo... like most modern 3D APIs (DirectX 9+, OpenGL 2+, OpenGL ES2), there is little fixed function shading or texturing capability baked into the Flash 3D (Molehill) API itself.
The texture box demo uses a shader to do its texturing because it must use a shader to do its texturing. You can author that shader in a variety of ways, such as directly coding the AGAL, but we think Pixel Bender 3D provides a less low-level, hair-pulling way to do it.
Modern, programmable 3D hardware is awesome and it completely transformed the way folks do 3D on the desktop. Mobile is next. Unfortunately, the initial ramp up with shaders is a bit steep.
Best,
Chuck.
