I recently bought a new laptop with Windows 8 on it and noticed that it was turning itself off if I wasn't using it for 20mins and it was plugged in. I had selected the Power Options so that I selected the option for the laptop to never go to sleep if the laptop was plugged in so I was confused why this was happening.
I knew the laptop was turning off rather than just going to sleep as my keyboard and mouse were not waking it up and the laptop was going through the boot sequence when I pressed the power button.
It turns out that Windows Hibernate was turned on by default and was overriding my default power options. Once I knew this it was easy to turn this feature off.
[UPDATED 15 Mar 2013]
Apple has finally released the trackpad drivers for Windows 8! It's not as straightforward as I was hoping as the BootCamp 5 install fails but it's quite easy to get it working manually. If you download the bootcamp drivers (http://support.apple.com/kb/DL1638) you might run into an issue where it tells you that "Only Windows 7 can be installed" on your macbook or "x64 installation is not supported". Luckily, all you have to do is run the driver called AppleMultiTouchTrackPadInstaller64.exe and it will update the trackpad drivers for Bootcamp 4 if you have that installed.