Maybe I'm missing something, but I just don't get MD. * The name: What do a bunch of geometric, flat-looking, solid colors have anything to do with "materials." "Material Design" always makes me think the direct opposite: skeuomorphism. * The look: It goes way past "clean" and "elegant" into "bland" and "childish." I don't want a bunch of tiny buttons with indecipherable icons and pastel colors. I want well-organized…
I don't know why you'd use Material Design for a website. I thought that the purpose of Material Design was to provide a common design language for Android Apps, like the Apple Design Guidelines do for iOS apps. Moreover, Material Design, with its simple platonic shapes and solid colors, seems really targeted towards mobile use. Simple shapes and solid colors can be easily implemented with vector graphics, which means that it's easy to render them in a resolution-independent fashion.
My criticisms of material design come from watching inexperienced users (e.g. my parents) attempt to interact with Google's Material Design apps. My dad refuses to upgrade his Android 4.0 HTC phone specifically to avoid the newer versions of Google Maps. He finds the gestures to be undiscoverable and doesn't like the fact that it takes two to three more swipes to access the same functionality. This is especially a problem if you're using the phone one-handed, while walking around or driving.