What was the most difficult part about it?
A tie between 1) answering the questions on the application and 2) taking a red eye from San Francisco to NYC for the interview and then flying back at 5pm the same day knowing that I had to miss school and work. The flight was physically taxing and also costly...the questions on the other hand were intense because that's what the departments are looking at when they are choosing and since they know nothing about you you have to do your best to cram as much of who you are into those three questions.
And just to elaborate, that the questions really are everything. Like any good job application, don't clutter it with unnecessary information. Make every word count.