The first thing I looked for was data export and import. I have an export from google contacts I'd like to import to get started quickly. I would also like to know that I can get my data out to use in other applications (a table for the activity logs joined on the relationship's ID, a table for the relationships, etc.).

The "Edit" link under "Personal Information" should also be Blue, like the "Add" links under the other sections. It took me about 40 seconds to figure that out because of the confusion.

Editing reminders would be useful. More flexible reminder timing (things like "end of the month", which could be more or less than 30 days apart, are very useful).

You should be able to select an existing Person entry for the Significant Other field. Also, if you add somebody through the Significant Other field, they should show up as a person.

You should also be able to delete a Person.