CD is a little loud but nothing terribly annoying.
I had to do some sort of stand on one leg, close my left eye, hold power button in, unplug, plug back in with power button depressed thingy one time.
When it rebooted the FAN was on FULL BLAST. It was the loudest computer fan I've ever heard. Ever.
Two more reboots and it was done. Apple told me that it was because after that type of restart the OS hasn't yet rebuilt the "fan control" settings or something like that. But I'll tell you-- it was like that a LONG time.
I rebooted... same thing. Third reboot and it was back to normal.
Other than that, my iMac is the quietest computer I've ever owned.