Judging by our latest poll, nearly half of TR readers still shut down their PC when it's not in use. Those folks will no doubt be happy to hear that, with Windows 8, Microsoft will reduce boot times substantially.
The company says it has implemented a "fast startup mode" that's a "hybrid of traditional cold boot and resuming from hibernate." User sessions are closed, just like during a traditional shutdown, but the kernel session is hibernated. That kernel session has a small memory footprint, so it can be written to the disk and loaded back into memory at startup much quicker than a traditional hibernation dump, which includes user data and is "sized by default at 75% of physical RAM." (Kernel-only dumps, by comparison, are "typically" only 10-15% as large as the amount of physical RAM in the system.)
The result on systems with solid-state drives is quite remarkable, as you can see below:
Users will still have the option of doing a full shutdown or reboot if they so choose. Nevertheless, the new, fast shutdown mode will purportedly still "freshen up" drivers and initialize new devices, so even enthusiasts who often tinker with hardware might be able to use it more often than not.
Check out the full MSDN blog post by Microsoft's Gabe Aul for more details about the new startup mode.