I bought a 27" iMac 16 days ago.
I got the 27" quad-core i5 model that is the highest-end model available at Apple's retail stores. Purchased it on Black Friday to take advantage of the sale.
It's behaved absolutely flawlessly so far - superbly fast and the screen's a gem.
Best computer I've ever owned.
I like buying retail so that if there is something wrong I can simply exchange it for a new one. Pity that prevented me from buying the i7 model, but it's less than 10% faster than the one I have.
For some reason Apple is very efficient making the all in one machines. It cost US$1,899 and costs far, far less than the equivalent Mac Pro without a monitor. Even the combination of a similarly-specced Dell with a comparable resolution monitor is a few hundred dollars more expensive.
I'm sorry Apple's having trouble building them, but the machine itself is first-rate and I'm extremely happy with it.