As a corporate IT Director with a lot of years overseeing Apple products, there is no doubt in my mind that Apple's quality control has suffered in the last three years or so. Here's some evidence to support my position: businesses generally don't buy extended warranties. Though they sometimes make sense for an individual, it almost never makes sense when you have 300-500 computers. The cost of the extended warranties never exceeds the amount you're paying in repair costs in a given year. Until recently, that is, for Apple equipment. My staff and I examined our outlay for repair services and downtime in fiscal 2008 and realized that we would have saved money, time, and aggravation by purchasing the extended warranty on all Apple equipment going forward. That was not the case for our Dell and HP gear. Failed hard drives, logic boards, and power supplies have become nearly epidemic.
So yes, Apple has a quality control problem right now, and I hope they solve it quickly.
Apple's Quality Control Is Overloaded