Build used: http://graphicall.org/45
I recently noticed that this option only appears whenever I have Cycles Add-on enabled (using a Cycles build). What I think it does is it shows you a material preview on your viewport instead of just seeing the default 'Viewport Color' as shown under the 'Settings' subcontext under 'Material'. As far as what I can see, the 'Material Viewport Shading' reflects what you have as 'Surface Color'. However, I am not 100% sure if this is really the case. If anybody could confirm, I'd appreciate it. :)
(click image to enlarge)
I noticed recently this new (or was I too outdated to even notice?) 'Material' viewport shading (see screenshot below). Clearly, what is this used for? I regularly use Textured, Shaded, and Wired, and was wondering if 'Material' has a better option elsewhere.
I'd love to hear your opinion. ;)