Sit down 100 randoms from off the street, ask them if "companies having your data up to date" is a big problem for them. The ask them how high up their list this problem is, if of course it actually is.
If I understand this right - not only do you avoid having to fill out the same address forms over and over for different services, you avoid the monumental task of making sure all of your information is up to date on major life events like moving, marriage, etc.
If I could avoid typing my shipping addresses in every online order form sourced from a trusted place (browser auto-fill is shit), I'd use the service in a heartbeat. Only updating one service when I move apartments? Sign me up.
If I could avoid having to fill out twelve forms - nearly identical for the first half of the page - every time I went to the doctor, that'd be worth $20 bucks a year from me.
But I'm pretty sure that developing a HIPAA-compliant system, and then convincing every doctor's office in the country to switch to it won't be covered by a $20/year subscription fee.
My money is on "not very high".