I'll give u the truth since I've had my original MBP replaced by Apple.
The Terms and Conditions state that the same problem must be repaired/replaced 3x without success before the merchandise can be replaced. This has to happen all within one year.
In my case, when the main board on my original MBP (w/ the upgraded GPU) needed replacing 3x w/o success, they replaced it with the lowest available UMBP.
I am not clear whether they were suppose to give me the UMBP w/ the upgraded GPU or not, but either case, I was just stoked that it got replaced. I ended up paying $500ish for the upgraded version.
If I had to guess why my MBP didn't work w/ 3 new mobos, it's because the techs didn't spend enough time testing it pre and post repairs. So, I think I got lucky.
I assure you that, in MOST cases, many problems will be resolved the first time around unless there's some sort of user interference, or exceptional case like mine.
They are not very generous about replacing your merchandise, so prepare for your item to be inspected thoroughly.