Instead of relying on custom, OS specific, proprietary plug-ins, they can now easily build and maintain their apps using a few simple JavaScript APIs and have the browser do the heavy lifting.
A lot of people have voiced their concerns over Microsoft's use of "touch-based" UI with Windows 8. In an attempt to gauge how the "average" desktop user will engage and react to Windows 8's Metro design, lockergnome had his dad sit down and use Windows 8 without any previous instruction.