Dear Vegangirl!
From experience, I can tell you that applying ED is basically adding to the risk of applying. I applied ED to UPenn which I love so much. I was deferred to regular admission and now I am quite late in the application cycle. I am not sure if I regret it though, because I am going to add much more to my application during the year especially my grades which are much better now. I had a bad semester this past Spring due to surgery and other things which may have been why I was deferred. I think UPenn wants me to show that it was just a bad semester and that I can bounce back. I think applying ED is good if you know exactly where you want to go (go see the school, speak to students, make sure you are 110% sure you want to go there) and you have been in contact with the admissions office for a while. I spoke to Gaye Sheffler, the Director of Admissions and Fin Aid, for at least 5 months or so before I applied ED. I took the risk and now I am applying late which is not totally bad because most of my schools are non-rolling. If you will be applying to mostly rolling schools if you do not get in ED, then it will probably hurt you because you will be rather late in the game. However, you should be slightly ahead of the August MCATers because the school has to tell you by Oct. 1st if you are accepted or not. So you can immediately send out your AMCAS to other schools and start the process. My pre-health advisor advised me not to do it and I guess now I am paying for it. At least I got deferred. Most schools do defer you to regular decision if you did not get in EDP. Then if you continue to show your interest and update your application, you may have a better chance of getting in. That is what I am doing. I really want to go to UPenn so I am showing my continued interest. I sent in a new LOR and will probably send 1 or 2 more, will send in my grades for this semester, and will send in a letter of intent to tell UPenn it is still by far my # choice. In retrospect, I should have just applied regular admission and then sent a letter of intent, but I really felt like it was a good thing for me personally. Sorry for the stream of consciousness. Please PM me if you have any specific questions.
-DrJ2B