What's Microsoft got to compete with the MacBook Air's near-instant on? According to this recent demonstration from its Building Windows 8 blog, the ability to take a machine from fully powered off to booted up in just under eight seconds.
The key change behind the improvement? In Windows 7, all user sessions are closed, as are services and devices in the kernel session. Windows 8, though, doesn't close the kernel session. It puts it in hibernation mode. By writing the kernel session to a disk—instead of having to restore it completely with every start up—Microsoft has seen improved boot times of 30-70%.