I don't know if I'm the only one, but when i'm just casually using my system. The screen would dim down and i can't get it back to normal until i either put it to sleep or restart it. It's like as if the LED back lit is ran out of power.
In my case this was the first symptom I observed. Two days later the screen went to a massive number of multicolored lines rendering it useless. A restart would restore it to normal for an hour or so before it would act up again. AppleCare said they hadn't heard about it. I took it to the genius bar where they were shocked to see how bad it was.
They ordered a replacement computer for me. Two days later they had it for me to pickup. I used it all day today and so far it's only acted up once. Shades of the ordeal I went through with my iPhone 4.
Now on my fourth returned iP4, I seem to have one that works. Only time will tell. My confidence has been greatly reduced. Apple is living in denial.
Sadly Apple seems to be emulating Dell.