We know Windows 8 is promising faster boot times and our testing largely bears that out, but that poses a potential minor challenge: you won’t have much time to get to the BIOS menu if you (say) want to alter the boot order to use a USB drive. Fortunately, Windows 8 also lets you access these options from within the OS itself.
The Building Windows 8 blog notes that devices with UEFI firmware will also be able to change those options from within Windows. It’s a small shift but a sensible one, especially given how arcane working through BIOS menus feels these days.
Reengineering the Windows 8 boot experience [Building Windows 8]