hm generally i would not say "dont get a iMac 27 " because they are rubbish "
some of them do work fine , one of my mates had its iMac 27" number 4
before christmas and its working perfectly without any flaws , so apple is able to deliver a good one ,
so i guess its only a matter of giving apple a bit time to sort the problem out with the manufacturer of the screens , harddrives , .....
or maybe they can just swap the supplier, if they are not bound with contracts