Oh how true...
Being an early adopter is never the most rational response. Of course, having seen a 27" iMac, you can understand irrational responses (it really is something to behold). It appears this issue is only on the Core i7 variant, others are fine (well have the normal number of DOAs - this happens with all products).
Of course, this problem is made even more annoying for those affected by the simple face that the Core i7 is a build to order option - and a popular one. You can't get it swapped from stock, and replacing machines is adding to already long(ish) lead times.
However, given all this nobody at Apple has denied the problem, and customers have been told exactly what kind of lead time to expect. I don't really see what more Apple can do. Clearly Apple will also want to understand why this fault is afflicting new systems and correct the problem (you can see that such an effort will do nothing to speed up the lead times).
So is the iMac Core i7 a nice machine? Yes. Should I buy one now? Well if you're really in need of it, sure... But personally I'd hold off until the new year, let Apple address this. This kind of issue happens in the computer industry all the time, the problem for Apple is they have "iconic" brands and the iMac is such an iconic brand that problems like this get noticed. If we were talking about some HP machine with some cryptic number for a name would this be as interesting? (Would El Reg use words like Fanbois or "howling" - no, they probably wouldn't even report it, because nobody would be interested. Given HP's quality control it would be hard to notice that any particular machine had a problem more than the normal shoddy junk they barf out anyway).
So the original commenter was right - being an early adopter of ANYTHING is a risk, sometimes it pays off and you get to enjoy a product before anyone else other times ... you get to talk to technical support (which is rather less fun).