Cards usually also allow you to request a chargeback against defective goods for which a merchant refuses to make you whole. In this case you could probably call up Amex or whatever and say "I bought a laptop that is defective within the warranty period and apple refuses to RMA it, here's the proof..." and they'd do it no questions asked.

I've done both of these things with Amex and Chase and it's usually a painless process for each. With the chargeback route, however, it's common for companies to retaliate by closing your accounts or otherwise refusing you service until you reverse the chargeback. If you actually tried to chargeback the macbook I wouldn't be surprised if you found yourself with a "your iCloud account will be closed in 30 days" email. When I charged back a local CSA for refusing to cancel my subscription without an onerous phone tree despite multiple emails I received a voicemail saying, very politely, "Your account is now closed but you will be banned from ever opening a new account with us in the future."

Fine by me...