I've had my motherboard replaced twice due to this issue. I bought AppleCare, so they have to replace it. I am amazed to hear that they are not handling this under the standard warranty. Thats fucked. This problem is most certainly real and Apple is seriously underestimating the Internet if they think they can ignore it. If you are looking at a new Apple I would highly suggest you factor the full cost of Applecare with screen coverage into the price when you consider the costs.
Apple iBook Logic Board (motherboard) problems: Flickering screen? You're not the only one.