EDP varies from school to school, and how they use it also varies.
I did EDP, and had a good experience. Also, everyone in my EDP group (18 persons) got admitted. However, the lowest possible MCAT to apply EDP was a 30, with nothing lower than a 9. GPAs were also a minimum of 3.6 or 3.7. So the worst person in the EDP group was as strong as the average matriculant at our school last year.
Don't apply EDP if you think you will have a tough time getting into school. Use it if you know you are a good candidate, and you have one school that you want to go to more than others. Also, do this only after finding out (from the school, an alumnus, or a person of good knowledge) whether or not your school takes their EDP seriously. Some schools have EDP but rarely admit people from them. Others don't notify students when they should (right away). I have read some real horror stories in this regard.
*Do your background investigating
*Apply EDP only if you are a strong candidate; don't EDP if you are trying to make up for weakness in your app by doing EDP. It works (barely) in undergrad, but not at all for med school.
*Apply only if you won't be sunk if you get rejected & have to apply late to other schools.
I knew I had a really great chance of getting in, and I only wanted to go here, so I did EDP, and am glad I did.
good luck!