I have a personal policy of purchasing Apple Care each time I buy a new Mac. It's great to have if you need it, especially now that Mac laptops are more like sealed appliances.
I don't mind paying for it even if I don't use it. Finally, it's good to have when I give away the computer to family or friends. Upgrading every eighteen months, I go through a fair amount of new Macs.
iPhone's, iPads and other purchases I make without buying Apple Care.