Exactly, Apple is hardly immune from poor QC at its overseas manufacturing facilities or the vendors it uses for subsystems.
No, they're not. But on average, they source good components and have good factory QC. Not perfect, but well above average. That doesn't mean they're unquestionably the
best in the world, but they are very good.
You can search for surveys from PC Mag, Consumer Reports, and any number of smaller outlets on the topic, and you'll find that Apple is usually in the top 3 or so (usually in competition with Lenovo/IBM, occasionally Sony, and somewhat surprisingly in the last year Asus). They're consistently ranked quite a bit higher than Dell, HP/Compaq, Gateway, Toshiba, and most of the other big-name brands.
Notably, they almost always rank at the top of customer support satisfaction--short wait times, quick and polite service. Based on my experience with Applecare vs. Dell support (or, for that matter, more or less any company I've ever called on the phone with a tech issue), I can see why.
That said, I also base my opinion on an admittedly small sample of the several dozen computers I personally manage at work or see come through my hands doing freelance tech support. Apple computers are not immune to problems--I've had hardware failures with my personal machines, and seen plenty of others--but they're less likely to suffer from them on average than other manufacturers I have experience with.
Regardless, I do think it's a little unrealistic to get irate about a hardware failure on a 4 year old machine, even a high end one.