Sorry, long post! Since mid-July, I have been having some big problems with my Late 2012 iMac. Now, I absolutely love my Mac and am really upset that after nearly two years of working just fine, things have started going wrong recently. It all started when I was browsing the web and watching YouTube and iTunes, Mail and Messages were open. Suddenly, the computer appears to turn off, as though someone had pulled out the power lead. I check the connections and it's properly connected. I unplug everything bar the power lead and attempt to turn it on. Nothing. So I unplug the lead and connect it again. Nothing. I unplug it at both ends and then it turns on. Something clearly isn't right here. It turns off again soon after. I run Apple Hardware Test which comes up with no issues found in the quick version. In the long test it turns off again. I reset the SMC and zap the P-RAM. It works for a little while then powers off again. The long and short of it is, I contact Apple Support and it gets sent to AMSYS, a respectable 3rd party repair centre. They can't diagnose the fault at first, so they call me. I tell them to wait and throw everything at it that they can because something will happen. Eventually they notice an issue with the Graphics adaptor. It's all built into the logic board so they order a new one of those. This is over a weekend so there's understandably a delay. I cannot fault AMSYS for their communication by the way. On the Monday, a new logic board is fitted, and the machine is put through it's paces and a healthcheck is performed before returning it back to me. It passes all tests according to the checklist when I receive it and they've not only cleaned it up, but have also put that film on the Mac that you'd find on a brand new one. I am happy and convinced that things are OK now. Things are great, for about 2 weeks of on and off usage. But... here I am again without a working iMac. It continues to just power off as though someone has pulled the plug, and not turn back on again. It has again been sent in for repair, and I probably won't see it for at least a week. Thankfully it's still under the extended warranty, but Apple insists on repairing it still, even though a *brand new* logic (main) board had been fitted in an attempt to solve the problem. I have exhausted all the main support channels today, after getting through to a Senior support agent. She assured me that it should be repaired because it is a hardware issue. As if I didn't know that already... I've ended up emailing Tim Cook and his team to see what can be done about it. Clearly the machine is no longer performing to the advertised standard when I bought it back in 2013. Two weeks later after having it back and the same issue continues to loom. I just don't know what to do at this point. But I do know this: I want a replacement. Am I being too demanding? How many times does it get 'fixed' only to break again? At what point do they think about replacing it? I spent a premium on an Apple computer as I believed I would get a superior user experience, and for the most part I have... until now.