I know that this is only one example, not representative of the whole population, and the exception rather than the rule, but one of my mates took an OCR History exam in the Jan 12 exam season, and his module grade went up from a low C to a low A* after a remark.
Luckily for him, he's an A/A* student, so he knew that he had to get that script remarked, but it's completely unfair on those who don't know what they actually should have achieved!