You mean flickering like this, right?:
http://www.youtube.com/watch?v=OwGkdOV37qg
It's the WiFi.
It seems to happen to a greater or lesser extent on a per-machine basis. Consensus seems to be that it's a shielding issue...the WiFi antennas are in the display bezel and somehow when the WiFi is in use it is screwing with the video signal (probably as it comes over the ribbon cable from the logic board).
Mine also does this, but it's nowhere near as bad as the guy's in the video. In my case, I actually have to be moving a significant amount of data before it happens (watch a streaming video or do software updates or something), and even then it only happens once every once in a while, usually right after the download starts, and then it settles back down.
If I turn the WiFi off and plug my Apple Ethernet adapter in, problem goes away.
I've heard tell that some people got their screens replaced and it solved the issue for them. I've also heard that it only seem to happen to some people when using a specific WiFi channel...some people have changed the channel on their router and the problem went away. (Of course, this doesn't prevent the problem from coming back if you are using your computer outside of your house on somebody else's network.) And other people have said that when they got a dual-band WiFi router capable of 5GHz, as long as their rMBP was on the 5GHz network, the problem went away.
-- Nathan
