Tom, considering Apple held a press conference due to massive criticism about another product's reliability in which they stated the return rate was 1.7% I think it's pretty safe to assume that the iMac return rate is much lower. If the iMac had anywhere near the iPhone 4's perceived % of units with problems the press would be all over it. So personally I think the quoted 1% figure is high.
Did you talk of the faulty machines, or a return rate? These are obviously two different things.
Some people simply don't see (or hear) a problem, if case is not extreme, other will tolerate it.
But if somebody wants a "perfect" machine and pays attention to the screen color, and light bleeding, and whistling sound, and HD clicking, the single replacement quite often doesn't seem to solve the problem.
Mind you, each replacement is not really fun for the owner, it is usually associated with a long installation process, testing, calling the support, cleaning, packing, driving, waiting in the store, waiting for pickup and delivery, unpacking and agonizing what there will be this time and what not. Out of thin air I'd say not many people do it lightly.
The most worrisome are multiple reports of multiple replacements - something which should be extremely unlikely if indeed only 1% of the units had a problem worth replacing, hence my conclusion of either higher problem rate, or redirecting of the faulty, returned iMacs as replacement units.
Tom B.
