My July 2007 MBP SR 2.2 would have been fine if I had posted in this thread back in May, but it just started freaking out two days ago (it's been really hot lately). I suddenly got a bunch of pink pixels all over the screen, computer froze completely, and then i got several kernel panics while trying to reboot. Its working off and on lately, so I'm bringing it in to an Apple store tomorrow night.
Most of the time, my computer use is pretty mild, email, movies, itunes, Matlab, VMware Fusion, youtube, but every once in a while I get into a game for a few weeks, CoD2, Halo, things like that. If the replacement motherboard lasts another two years, i MIGHT be willing to give in and get a new computer by then, but only 4 years of use is pushing it for me.