I can only notice it on grey backgrounds and the Dashboard, and it's not as noticeable as in THOPMedia's picture. I read the Apple support article for the link posted by jackvega, which makes it clear to me that Apple is saying this is not a defect but an "expected" behavior of IPS displays. Acceptance of that explanation is likely a personal decision.
I work from home and use my iMac for very long periods. I had the screen saver disabled and let my screen sleep after an hour, so all night long. Yesterday I changed it to go to the Flurry screensaver after an hour and then sleep at the 3-hour point, so 2 hours worth of screen "wiping."
This morning, I can't see the persistence on a grey background (or the Dashboard background) anymore. I realize once you see something and expect to see it, your mind may put it there (like a sign you believe reads gas or food ahead on the highway until you get closer and see it's something else entirely).
For me, Apple's solution works. Sure, I'd be happier if there was zero persistence. But the tradeoff is an incredible image with 178 degree viewing angle. I'm satisfied.
Your situation may require more screen saver time. Apple says "To clear the persistent image, allow the screen saver to run for approximately as long as the image was being displayed." I'd suggest letting it run all night at first, then backing down to follow Apple's rule.