HealthVault has really stimulated great discussion on the issue of PHRs. A good part of the discussion is on the viability of the PHR concept and if PHRs concept will really "take off".
The vast number of PHR users are likely going to be the "worried well" (hypochondriacs) or those people with chronic illness who like to track (or in some cases, obsess) over their health issues.
The elderly, who probably would have the most to gain from a PHR for its ability to track long medication lists, multiple doctor visits and hospitalizations, are the same people who would be less likely to use a PHR. And this is not just because the elderly are not computer literate, but because of the usual age related health problems, such as low vision, early dementia etc. We will need to depend on the care givers to manage their PHRs.
To most people however, healthcare is something they hire someone else to worry about (the doctor) in much the same way we have a fund manager to manage our mutual funds. I suspect that it will be the “Quicken” types who will make up the vast majority of PHR users.