Do I want to buy Apple Care when I get my new iMac after the refresh? I'm not sure which of the four models I'll pick -- does your answer change depending on which iMac I get? If I don't buy it when I buy the machine, how long do I have to buy it? I've had a whole mess of Apple products before but never an iMac, so I'm hoping those of you with iMac experience have some extremely valuable input. Thanks and Fight On.