[qdmcg]

My thoughts: the essay isn't super important.

If your academic qualifications are boderline not good enough for a certain school but you write a memorable essay that stands out, it can certainly help you get in. Also, if you write a very poor essay (the only thing I could think of is one that is very inappropriate or one that shows you clearly put very little thought/effort/time into it) it could prevent you from getting accepted somewhere you may have gotten into.

Other than that, if your essay is just "normal/solid", I doubt it has too much effect on whether or not you get in somewhere.