I think it would be a waste of money. Just find a friend or MD who has some idea what the med school admissions process is like, and ask them to give you some comments.
A friend of mine was offered a job by Essay Edge, but decided to turn it down because basically, the "editors" totally rewrite the essays, and she didn't feel comfortable with doing that. In my opinion, if you've managed to get through college and get grades decent enough to apply to med schools, you should at least be able to write your own PERSONAL statement. However, it is essential that you have someone to at least give you feedback, so if you really can't find anyone decent to help edit your essay, then I guess an editing service could be worthwhile. Just make sure the end product is your own! 🙂