no, i just ask some people who already get their 27"2013 imacs and no problems found on any of the 8 pieces
As far as I know, 27'' LG IPS Monitor remains the same. Do you think QC in China became more "serious"? I hope so....
Let's see after a couple of months when the sample of "new" 27'' iMacs becomes larger (Also, keep in mind, many customers don't report actual monitor problems because in the beginning, they are mostly astonished by iMac capabilities).
PS: As I said, "replacing iMacs under warranty" is not a "happy game"...an expensive computer with high technology components shouldn't have problems with the monitor quality.