We have 55 iMacs and Mac Pros in our facility. about 10-15% have gone in for repair during the Apple Care period. These are heavy use computers, so I imagine the failure rate is lower for most Macs. So that is the risk you are taking. 9 times out of 10 you will not need it. But if it is an expensive piece of equipment that you would be hard pressed to replace, it might be worth it. The only thing I have ever gotten Apple Care for is my Mac Pro, never got it for any of the other apple products I own (iPods and mini's for the most part).