@UCLSMac
my MBP started crashing about 3 months ago with SL and I DID take it to apple only to be told there's nothing wrong. similar to another person a few posts ago. The technicials are clueless and simply run the hardware test which we can do on the disk. They probably spend an hour max on the problem and if they can't see a crash then your SOL.
@elio.dainese Chips certainly can have inherent problems. Just because "they are silicon" does not mean they are perfect. There are many manufacturing problems which can occur. These chips can either be scrapped completely, certain features disable or fixed by applying higher or lower voltage to achieve stability etc etc. GPU's especially will be manufactured then tested for grading, and quality of the yield. Based on how they pass tests they will be thrown in the appropriate bin determining whether they are destined for the low quality price point or premium Overclockable variety GPU.
Bad yield GPU chips might instead of having say, a 8 rendering/graphic pipes, have 4 pipes disabled because they were causing faults or maybe they'd simply be cut to reduce heat. So instead of being a premium 8 pipe chip it becomes the cheaper price point 4 pipe chip. Also voltage vs clockspeed plays a factor.
There are even cases where video cards will have higher than expected yields so to fill the lower price point card allotment they will on purpose disable features like pipes through firmware. There are cases of users unlocking features in their cards to upgrade the card to a higher quality card via "hacked" firmware updates. IIRC a example of this was the nvidia 9500 unlocking to become the far more expensive (at the time) 9700. You could even buy these "unlocked 9500 to 9700" cards on ebay.
Thus, firmware DOES play a factor in hardware performance, feature set and stability through enabling/disabling certain features which were previously disabled to provide stability.
Anyway i think we have a case where some mid april 2010's 330m GPU's were marginally faulty but passed the "quality assurance" checks. Some people, like myself, would crash so rarelythat apple couldn't detect the issue and simply tell us "there is nothing wrong". After lion there was a possible firmware update which has inadvertently unlocked hardware features which were either disabled or untested and simply don't work reliably.
One final thing to think about: Another reason i'm certain its a hardware + firmware issue and not simply a driver problem... I bought my MBP mid 2010 at the exact same time as my work mate. We both have the same model. He never crashed in SL, not once. I started crashing many times after about 6months. Then we both updated to Lion on the same day. I started crashing immediately and upto 15+ times a day. He is STILL yet to crash. Please tell me how software could result in my identical machine crashing when his does not if its purely a driver issue and not hardware? We both have identical software how could it magically perform differently on his machine than mine?