It certainly helps- it is a good opportunity for an applicant who would otherwise be in the middle of the pack to grab a seat.
There is no harm in submitting an early decision application, even if you are on the low end of the applicant quality spectrum; you'll have your decision by the end of October, and if you are rejected, you've got time to apply elsewhere. If your heart is set on one particular school, give it a shot. The worst they can say is no.