Just wanted to warn other Macbook Pro / Nvidia 8600M GT readers that Apple will not definitely cover a video adapter failure, despite what they say in tech article TS2377. I took my June '07 17" MacBook Pro in to the local Apple Store a couple of weeks ago when my Nvidia display crapped out. Definitely this issue--display was black, external display was black, but booted into target disk mode no problem.
The Genius booted it from a special external drive which ran some hardware tests, then he connected the drive to another Mac and showed me that the diagnostic log indicated that the relevant Nvidia display adapter was not found. Since the 8600M GT wasn't found they couldn't cover the repair under the "extended" warranty outlined in TS2377, and I had to pay out of pocket. Of course the 8600M GT wasn't found--it had died!
So now it's back on my desk, complete with refurb logic board. Calls to Apple to try to get the repair cost refunded have gone unreturned for two weeks now, so I don't think anything's going to happen on that front, but at least others can learn from my experience.
The main lesson: if you have an 8600M GT equipped Macbook Pro be sure to get it in to Apple at the first hint of a problem (I'd suggest running Apple Hardware Test frequently). If you wait until the display adapter dies completely you're at the mercy of the local Genius as to whether or not it gets covered.
And, yes, I'm planning to sell my MBP before it happens again. I went through two replacement logic boards on my old iBook G3 (remember that fiasco?) and this smells like the same sort of runaround. That makes two out of the last three Apple laptops that I've bought that have been dogs (my PB G4 is still going gangbusters); I still think Apple's software is great, but they're not exactly winning me over with their hardware execution, nor their erratic (and in my case downright bad) customer support.