I have been having problems for the last little while with my BRAND NEW IMAC where it has been hanging for no apparent reason. I installed new memory and still had problems until it totally froze and wouldn't even recognize the HD at startup. I called apple and they walked me through some tests and finally a HD re-seat...nothing.
Josh, my apple helper, said that they would send me a new HD and to watch the mail sometime next week. This was yesterday, BTW. Today, I get a knock on the door with a Purolator guy holding my HD! Absolutely fabulous!
I installled the new HD and reinstalled tthe system software and, so far, no problems. I also called Apple today for some help with the install and got Josh again. He couldn't believe it either and he was very helpful again.
Just wanted to pass on that little tidbit about great service.