I'd like to know from the OP, what is the exact nature of the problem with your iMac? What's the severity and/or nature of the problem? It might shed some light on the Apple Store's response or lack of it.
The problem is that my computer does not power on. Nothing... nada... one day it was working fine... then suddenly I turn around and the computer stopped working. If you press the power button, nothing.
Yeah... sounds like an easy fix, replace the power supply. But supposedly that's been multiple times, along with a replaced logic board, replaced audio board, replaced cables, etc... and it still won't power on. ( It did work for 2 weeks, though the computer did shut down all by itself 2 times while in the middle of something. I finally shut it down for the night, came back the next day, and it wouldn't turn on)
HTH