Just noticed I have something very similar to what you are referring to on my 2 day old mid 2011 27" iMac. Just got it the other day and noticed a very small set of gray/blurred pixels near my dock. At first i thought it was just part of the "Launchpad" dock icon, but once it hid the dock and set a white wallpaper, I knew it wasn't. Its not crisp but rather shiny/blurred, like its under the glass.
So you guys thinking this is moisture and might go away? Going to give it a few more days and then take it up the the apple store if it doesn't go away. They would just remove the glass and clean it or replace the glass and not the entire machine correct?