Just thought I'd post this link to a blog post discussing some studies in Health Affairs regarding scheduling and task management (I might be twisting slightly the terminology employed!) in medicine... It looks to me like GTD would be very useful in those circumstances!
http://www.kevinmd.com/blog/2010/07/practice-primary-care-sense.html
http://www.kevinmd.com/blog/2010/07/practice-primary-care-sense.html