I would go tell Apple it is flickering. This will force them to swap the logic board with a new one. That will solve the problem and fix your MBP for the long run. I think that is a really nice machine, but if you are looking for an excuse to upgrade to unibody just do it. Nobody here needs to give you approval. Do what you want, it's your money. If it were me, I would have Apple fix the logic board which fixes the 8600 GT card.
Good luck.
The problem is it doesn't flicker all of the time. Just randomly. I bet Apple will say that they can't duplicate the error.
Everything electronic I won is breaking. My Onkyo surround receiver, my Linksys WRT54GL router (replaced with Airport Extreme today), my MBP (kind of), my Cable modem...etc. etc!