While medical school admissions committees don't expect you to be a budding Hemingway, style does matter. A better-written essay will always be more impressive. Here are some things to consider.
Generalizing is really bad. (See what I mean?) Your essay must
communicate clearly and effectively. This means that every time you write a sentence that could be used in any other essay, you need to cross it out and start over. For example, "I truly enjoy working with people "could be the opening line in an application for Fry Guy at McDonald's just as easily as it could be a statement about the profound impact you want to have on your patient's health.
No mistakes. If you are not one of those people who goes around making a pest of themselves by correcting everyone else's grammatical errors, you need to find one. Most colleges and universities have writing centers with free editorial assistance, or you can check the local college paper for teaching assistants willing to edit for food.
Everyone has an interesting style, and you need to write until you find it. You are who you are for a reason; you have to write until that reason becomes apparent to anyone reading the essay.
At some point, the reader will have to have a very clear sense of just whythey should let you into their medical school. Don't get so caught up in explaining your inner child that you forget to mention your desire to become a doctor.
Make sure your essay fits together. You shouldn't be able to move a paragraph or a sentence when you're finished.
Remember that your entire personality is not going to be reflected in this essay nor can you entirely offset an otherwise weak application. But this is your big chance to talk to the committee, so make the most of it. Spend the time necessary to draft and re-work your essay until it is the best measure of your writing ability and candidacy for medical school.