I'm unimpressed. It's uninspired and looks like a basic 90's system. First there was too much skeumorphism and now too little, there should be a balance. If the windows lose shadowing and definition, it'll take some adjusting to distinguish windows on top of one another (esp. as there didn't seem to be much of a border). Don't get me started on the Control Center left side slide out panel or the 10.4/iOS 7 dock. Don't go skeumorphic but bring back some polish. This should be named OS X 10.10 Mojave Desert, it seems to have about the same life.