I know that Rev.1 has a banding problem that's caused by a buggy firmware...
However, what I'm talking about is a panel problem.
Check out this photo below (its from a 24" iMac which uses an LG-Phillips S-IPS panel):
http://img264.imageshack.us/img264/7362/dsc00476yz9.jpg
Notice how on the left side there is a blue tint to the grey background and on the right side the color is more 'yellowish'...