YES. If you can manage to impact the adcom in the limited space pharmcas gives...then yes it can make you stand out, and can definitely help.
On the flipside, I did spend a lot of time on my essay, and consequently during the interview, was asked detailed q's about what I had written. So for whatever that's worth.
Edit: in terms of advice, think back to the last time you really cried, laughed until it hurt, or, danced like no one was watching. Then write about it.