Barclay's Bank that is connected to Apple's financing a purchase is one of the worst credit card issuers. Beware of them. Do a Google search and you will seen how hated they are.
I can't say I'm too thrilled with them, either. I purchased my Rev A through Apple and used the Barclaycard (I think it was branded as Juniper) primarily to get the iTunes gift card and deferred interest promotion they were running at the time. I paid it off in full and on time, but I do vaguely recall that the statement date on the card wasn't aligned to the date of my purchase from Apple, so it can be easy to miss the payment deadline. What surprised me is how quickly Barclaycard closed my account after a few months of inactivity. I'm not sure if they were using the financial crisis as an excuse, or if they concluded that I wasn't profitable enough.
It looks like MacMall uses WebBank, which also handles Dell's credit card business. I haven't read all their fine print but it looks similar to most offers I've seen.