I think that buttons with some kind of bevel/emboss - ones that resemble the ones people have seen on computers for the past 20 or so years, and in the physical

I think that buttons with some kind of bevel/emboss - ones that resemble the ones people have seen on computers for the past 20 or so years, and in the physical world for 100+ - are going to be more recognizable. Flat UI means a smaller visual vocabulary (usually, and maybe not the best chhoice of word but hopefully you know what I'm trying to get at), but it also means fewer clues for users. Once they've figured out the answer to "what is a button?" they're left with something free of visual noise that is mostly only useful while learning. (Anecdotally) For someone non technical, change is usually bad when it comes to interfaces. I think that simple and "easy to understand" is a great direction and have tried using flat and "ios7 color&font weight differentiated buttons" in some recent projects. I have seen teething issues when moving towards UIs where the visual definition of a button does not include some "quasi-3d" aspect. Simply differentiating by text or background color makes a lot of users apprehensive about touching things, afraid they will produce an unexpected or unwanted result. I've seen them adapt rather quickly, but there has always been some 'what do I press?' stage. Not exactly test data, but the results have been pretty consistent. EDIT: I should note that usually adding a stroke to just the bottom edge of a clickable button or a slight shadow/gradient usually helps. You can see this style in a lot of recent google products and I think it works really well (and I bet they tested it before deploying!). This method allows you to remove or tone down the shadows/gradients/textures from your navbars and other items without having them feel disconnected from your buttons.