I'll answer your thread title, because I haven't had a disaster.
Our pre-med committee exists of one person, the dean of our Arts and Sciences College, who has been doing this for a long time and knows a lot (not a common theme). We have to pick six faculty members to write letters for us. These letters are then submitted to our pre-med advisor and she forms a composite letter that is sent out to schools.
Basically, everything is student-outlook based. There is no reason for a bad letter since you are cherry picking your letter writers.