Windows 8 introduces a problem new to the annals of computing. Systems using the new Uniform Extensible Firmware Interface in place of the venerable BIOS and a solid-state storage device in place of a spinning hard disk may boot so fast that there is no way to for a human being to interrupt the process. No more F8 to get to the Windows startup menu, or F2 (or any of a number of other key combinations, depending on the manufacturer) to change system settings such a selecting the first boot device.
Windows chieftain Steven Sinofsky has a post on the Building Windows 8 blog detailing Microsoft’s response to the problem. Basically, any failure to boot normally automatically generates an option screen that lets you choose a response. Interrupting an otherwise normal boot can be accomplished through settings within Windows, then restarting.
Having spent far too many hours of my life twiddling my thumbs while Windows systems rebooted, this is one problem I am really looking forward to. (Of course, Macs have dealt with related problems for years by just having you hold down a key as you power up.)