If you put something on that zoom (or other prime), something like a close-up lens, or anamorphotic lens, that something would be the thing that is not a prime (and as a secondary makes the taking lens - whether zoom or not - the primary lens).
So my vote today for the most overrated feature is the word "prime".
By reading through this thread it becomes obvious to me that there's no right answer to the question, it depends on the individual and the type of photography he/she is involved in, what might be essential to a sports photographer, might be useless for macro, or architectural photography.