How many times can a script kiddie try the exploit in a minute? In a hour? In a day? I don't know the details on this exploit, but I expect the answers to any of those questions should range from the thousands to the tens of thousand attempts.
How many times does it have to work? The answer, of course, is 'once'. So if the exploit is as little as 0.0001% reliable I bet it can can lead to a rooted computer 100% of the time given the right circumstances.