FYI - an Australian government report into the doctoral students' experience and an analysis into the doctoral degree structures. Amongst other things the report discusses, I found this relatively small paragraph in the executive summary interesting:

"The large majority of students are positive about their doctoral programs. For some however the experience is at best neutral or mildly disappointing and for a small number fairly traumatic. Twelve per cent of students interviewed expressed dissatisfaction with their supervision experiences and five per cent had serious grievances."

http://www.dest.gov.au/sectors/higher_education/publications_resources/other_publications/the_doctoral_education_experience.htm