Hi rahulmathur9818,
Other than the "reinstatement fee" (which is currently $100), one of the downsides COULD be that most Test Takers really have no way to gauge the true strength of a performance other than some general data that can be found through internet research.
For example, if you scored 650, then would you cancel?
A 650 would be considered "below average" at most Top20 schools, even though it's about the 80th percentile overall. Some Test Takers would cancel immediately, but I can tell you that I've personally worked with people who've gotten into Harvard with 650 (or lower), so in THAT context, canceling a 650 would have been a really bad idea.
When faced with that type of decision, it's better to think more about the "range" of scores that a school accepts and not the average score of a school. It's also worth noting that Business School Admissions Officers are savvy - they understand that not everyone is an amazing Test Taker - if you have a strong-enough score and a strong overall application, then they'll consider you (and would likely grant you an interview to confirm their assessments).
This is all meant to say that you should only cancel if your score is far lower than the range of scores that your goal school(s) are likely to accept.
GMAT assassins aren't born, they're made,
Rich
