I would find it useful if we were able to toggle on and off individual material layers. For me, it would be handy in isolating things in materials that I want to fix / modify, and it would be nice for preview renders where you could turn off the more complex aspects of a material to speed the render up.
Re: Toggle material layers
Yep…thats on the wish list
In Studio MAX …
In Studio MAX they use the light bulb icon in many areas to turn on / off a single setting to evaluate its effect on the final. Could be nice.