How much does having a few publications help?

I am aware that having a publication definitely won't compensate for low GPA/MCAT; however, assuming that MCAT/GPA are within range or competitive for a school. Does having a publication really matter, even though roughly less than 20% of applicants have a poster presentation?
Source: Student Doctor Network - Category: Universities & Medical Training Authors: Tags: Pre-Medical - MD Source Type: forums