Hi all, I lurked last year and decided I would share my application experience for all you helpful folks.
Last year was my first time applying and I was in my first year of a PhD program. I'm in biological sciences. My reviews were terrible and I only had two reviewers, so I must have been near the bottom of the barrel. Some highlights from my reviews that will hopefully be informative for you, some of which surprised me:
1. Only 1 of 2 reviewers made any comment on my proposal. The one that did only wrote one sentence: that I should try to make the proposal more focused and on a centralized hypothesis.
2. Both reviewers said I had an outstanding academic record. However, reviewer #1 did not like the fact that I had two letters of references from professors I met in grad school and only one from undergrad. I thought that this would actually make my application stronger, but I guess it backfired. The undergrad mentor was a PI I worked with for 3 years and did a conference poster for, so I thought that would be good enough but I guess not.
3. #1 also did not like that I had a "5th author publication" as an undergrad. They seemed to think I did not explain very well what I contributed to the paper. I did talk about this research, but I think I should have explicitly said "I did X and Y which led me to contributing to Z publication".
Hope that helps people avoid some of the mistakes I made! I'm working to address these issues this year, but I'm not too confident I can go from a "2 reviewer" level application to a winning application.