Heads up! Before installing 8.1. . .
Make sure you have important drivers (like, say, those for your mouse or network adapter) on hand and easy to access.
When I woke up this morning to a fresh install of 8.1 (without prompting, it installed itself overnight after I thought I had cancelled the download) none of my 3 mice would work and my wireless adapter wasn't recognized.
Just a friendly heads up.