I am not sure what was more difficult: studying the material, writing the research proposal, assembling an exam committee, or completing the paperwork. But after (what seemed to me to be) a long oral exam, I was told with a hearty handshake that I had passed my university GBO (Graduate Board Orals) exam at Johns Hopkins University. There were five people in total on my committee: three in my department and two outside my department. The chair had to be outside my department, and of associate or full professor rank.
As a result of the questions I actually got some leads into new areas for my research, which I suppose is one of the better results of such an exam.
Now, on to the dissertation.