The differences from Windows 7 to Windows 8 are around a new user interface called Metro. The Metro display replaces the traditional "start" menu. Many apps are then optimised for the Metro UI which brings larger buttons and more intuitive menu options to reduce clutter. This is far better for touch operated devices such as touch screen laptops and tablet devices. The classic desktop and windows explorer UI are still there for desktop users.
Is this release of Windows trying to be all things to all devices? Perhaps Android will be a better OS for tablets as it's optimised to touch screen operation from day one. To decide yourself you can download the developer preview to run on and old machine, or as a virtual machine.
