SteelSeries drivers/software for all of their devices like mice, headsets, controllers, etc. is not compatible with Windows 8.1 and it will make your computer unbootable if you decide to upgrade. They are not sure when the 8.1 drivers will be released even though people have literally been asking them for over 3 months. Just a fair warning, don't upgrade to 8.1 on Friday with Steelseries Engine installed if you want to be able to use your computer.
Let me google that for you
This could be a huge disaster for the gaming community if many people update on Friday only to find that they cannot boot into Windows