it's been 3 months since i posted my original message and by using a cooling pad and being extra cautious i managed to buy myself enough time to actually raise some funds for a new laptop.
i was in for a nasty surprise today as I took the machine off its cooling pad and pretty much allowed the GPU to overheat by placing it directly on a table surface and running it under high load for a bit. that lead to a halt (the usual graphics freeze). i restarted. then the picture i saw scared me and i thought i had finally lost my mac. it was all random pixels and distorted lines everywhere on the screen. i shut it down again, allowed it to cool off, then booted it up, disabled quartz extreme, and restarted.
this is a funny situation as my machine now runs cooler than it used to, and the hit on the cpu is lower than i previously reported. MBP on my laptop as I write, and CPU at 54C (GPU at 48). it certainly makes the computer useable for browsing and casual work. i am yet to try it under really high load (Logic). i've also switched youtube to html5 so flash video is less in my way. hopefully this will buy me another week of time (since i really wanted to wait for apple's upcoming announcement).
i know this is no remedy, but as far as failures go, this is pretty much organic (i.e. gradually degrades), and i am actually quite fascinated with my failing computer. it has earned back its money (many times) so outside of ATI's poor manufacturing, and Apple's aggressive thermal design, I have little to complain about.
I don't expect Apple to suddenly send us each a new laptop, and this thread is our little support group here, so yeah, exercise damage control, and if you're after a quick fix, and don't use the 3D features of the card (like for games or graphics-intensive apps), try disabling quartz extreme. you'll recognise it's disabled by the look of the apple logo in the menu bar. it's ever so slightly different with QX disabled.