Beware! That is what I wish it would have said before I performed the update to my Mac Mini. After the update, everything seemed to be fine. Then, as fate would have it, the batteries in my Apple bluetooth mouse went dead. So I replaced the batteries, and my mouse quit working. Well, not entirely. The button still worked, but the mouse no longer tracks. I tried quite a few things, but nothing seemed to fix the problem. So, I am now using an extra Apple Pro wired mouse on my Mac Mini until I can find a resolution to the problem. Anyone out there with a similar problem and a fix for it, please let me know.