It sounds like you are in a terrible situation, and you've been polite, and patient far longer then I would have been.
I'm not a switcher yet but I cruise mac forums everyday and am planning on getting one soon. So while I can't help you with your issue, I promise you I've done a LOT of homework on macs AS WELL as their customer support. Which makes or breaks a company in my opinion.
I've heard very good things about apples support, very very very few really upset people, so honestly my only bit of advice is to either keep trying to talk to apple and pray that they help you. Or sell your mac on ebay and let apple know they have lost a good customer to the shinnanigans over the laptop.
None of that will really matter to them, but you can only do so much, and so often where companies are concerned they really don't care about their customers and they are only going to pretend they do to a certain extent.
It's obvious that you are very upset about the situation which does of course mean you may be over exaggerating but it's obvious you've had a LOT of problems that should have been handled long ago. I'm truly sorry for all the time and aggravation it's caused you, because I know how you feel.
EDIT: .. You're problem is worked out now, and now nothing I wrote matters lol. So anyway, extremely extremely happy for you that they replaced it, and I will really cross my fingers that it works good for you.