I decided to build a family tree site with Joomla 1.6 to make use of its ACL feature. Joaktree is the ideal component to compliment this. Getting your GEDCOM file set up takes a bit of care, but the documentation is very good and detailed.
I particularly like the way you can integrate custom articles with your tree members. I had a query about article linking, and the developer answered back in hours with a solution. You rarely see this response with commercial support.
I have no hestitation in recommending this excellent component.