This is the "fish-or-cut-bait" point of my time with my MacBook Pro. It's been sent back to the mysterious place where they repair them.
A few days ago I turned it on and got only a kind of psychedelic static on the screen. I took it in and the diagnosis is either the screen failing or the motherboard failing. The motherboard is what I'd suspected all along. So far I've had the hard drive and the RAM replaced already. There isn't that much more left to replace.
So what will be the outcome? I'm on total warranty for about another two weeks. There are several possibilities. First, the guys could discover what's wrong and replace it. At this stage, they (those who are in charge of making these kinds of decisions) might junk it and give me a new one. Either one of those things would be fine. Also, they could try to stall me until my warranty runs out. I could kind of counteract that by extending my warranty, but I can't get an "everything" warranty that includes replacing the computer.
In any case, the ball is in their court. I should hear something in a few days. If the worst outcome happens and I get back the computer only to crap out completely without a warranty I'll just go back to a Windows laptop. They're cheaper, and at least from my experience, they're better-made.