The Windows 8 UI is completely flat in what used to be called the "Metro" style and is now called the "Modern UI." There's no pseudo-3D or lighting model to cast subtle shadows that indicate what's clickable (because it looks raised above the rest) or where you can type (because it looks indented below the page surface).
I haven't used the new OS but I've noticed this glaring flaw of Windows 8 in review videos. When users open a screen, everything looks flat and similar; it's impossible to see what is clickable and what is not.
I usually have to do some of my work at home. I prefer doing that on my desktop PC. The screen real estate is such a nice luxury. Unfortunately, Microsoft redesigned Windows for tablets and sacrificed the advantages inherent with large monitors.
The situation is much worse on regular PCs, particularly for knowledge workers doing productivity tasks in the office. This used to be Microsoft's core audience, and it has now thrown the old customer base under the bus by designing an operating system that removes a powerful PC's benefits in order to work better on smaller devices.
Why did Microsoft even have to subtract the ability to open and view multiple windows at once? They could have given the users the option of using the classic (Windows 7) way of dealing with windows.