Perhaps it's nostalgia, but I feel like the initial "material" concept—UI components being like stacked paper—was better realised in 1 (and 2) than in 3. It was

Perhaps it's nostalgia, but I feel like the initial "material" concept—UI components being like stacked paper—was better realised in 1 (and 2) than in 3. It wasn't the first minimalist design framework, but the spec was notably thorough in a way the new one isn't. I also preferred the barely-rounded corners and standardised colour palettes, but that's more a matter of taste.