That text shading is pretty nice, and extruding compound shapes like that and getting all of the parts properly stacked/layered is no simple task.
As you’ve probably seen in the beta builds, I’m working on new shading methods including gradients for curved surfaces. I’ve been working first in implementing the new shading in live object (Transformations panel) extruding, but Illustrator doesn’t have true multithreading so things can go haywire quickly. I’ll likely disable shading in extruded live objects at least for now in order to continue work on the improved shading.