Windows 8 is easier to use than OS X.
When the iPad first came out, people said nobody would buy it because it couldn't be used for "real work" and it was too "dumbed down." People said laptops would be preferred. Now, people are making the same mistake by saying nobody wants touchscreen laptops and desktops because they're too simple.
Touchscreens are more intuitive and easier to use than mice and trackpads. They're also more productive and accurate. Drawing with your finger, for example, is far more accurate than drawing with a mouse or trackpad. Touching UI elements directly is more intuitive than moving a cursor over them. Games are more accessible, which is why games like Angry Birds and Cut the Rope have been so successful.
Because of touchscreens and Modern UI, Windows 8.1 is now easier to use than OS X. This will give Microsoft an advantage until Apple catches up.
Touchscreens will replace mice and trackpads, and motion sensing will replace touchscreens.