My .02 cents? The guy whining that he bought his in December and wanting a new one is being totally entitled (I don't care he claims the clerk told him the new one when it was out wouldn't be a big change). And I was disappointed to see that he got his way by whining (apparently he found a spineless manager).
This guy? I think in the name of good customer service, since he's been having such bad luck with getting a new computer that works right, Apple should happily give him the newer model. It's not even that he got one defective one, he's gotten two. That certainly would leave a bad impression on me about Apple quality. If I were Apple, I'd at least try to make it up and say, "Well, we care and we want to make sure to leave you with a good impression of us." Going above and beyond is a great way of doing this. Sometimes you can turn a bad customer experience into one that turns the customer loyal. Messups are the best opportunity to really prove to the customer that you are worth their loyalty. It's all how you handle it.
Anyways, the difference between the two is the first guy Apple did not mess up, he did. He got impatient, got his computer ahead of time, took the chance he wouldn't like the new models (or wouldn't care that much), and lost.
The second one? Apple messed up, twice. Sure, defects are sure to happen every now and then but to have it happen twice? That's embarrassing. I think it is a good idea on Apple's part to give him a little extra for his trouble.