Some time ago I looked at an article on performance of cards by Rob Galbraith. Unfortunately it does not include the 800x Lexar card. I assume that the article was written before the 800x card was available. As I recall the actual performance of the cards was not necessarily in line with the specifications stated by the manufacturer. Therefore, as you suggest, I am not at all confident that one can rely on the manufacturer's specs. That is why I am hoping that some fellow Nikonians who have used these cards can provide some real life information that will provide a basis for deciding if the 1000x cards are worth the extra dough.