i can't see it being a major issue,
one thing sites like this are good for is showing up major problems with a car, as people only tend to log on with a problem.
and with several people on high milage, and the number of memebers on here; a pattern would normally be visible now. this forum seems to know the main issues this car suffers with and most are pretty minor.
myself and ekona both used to be on the mr2roc forum where we started to see a mojor pattern of engines blowing due to a dodgy valve seal (there was large debate over the cause, but many believed the pre-cats to be responsible) this is something that toyota have only recently agreed is an issue, before that they denied it. and it was only because of the forums bringing it to the attention of toyota GB.
i would think it is nissan doing a live engine check, looking at one that has been used in normal conditions and not just sat on a bench tester.