DT has a lot of potential as a contact manager (a CRM tool, essentially), but I am finding its functionality limited, and thus am resisting using it as such. I can certainly import Apple Address Book entries into DT. And while the imported address card will offer a link back to the original Address Book entry, there is no “syncing” between the two - changes I make in Address Book are not reflected in DT, and vice versa.
Bento 4’s Contact and Customer Manager template, on the other hand, does offer this two-way “syncing.” (http://www.filemaker.com/products/bento/demos/?homepage=bento_box_demo#contacts) Bento does not simply import and link to the Apple Address Book entries. It actually reads and writes to the Address Book files directly. Thus the Bento entries and the Address Book entries are always in sync. Such functionality in DT would make it a great CRM.