The following was written by Synium Software:
But MacFamilyTree 5.5 Public Beta delivers even more improvements: Users with huge family trees will appreciate MacFamilyTree's completely rewritten genealogy database technology. GEDCOM import, as well as viewing and editing of information in your family tree is much faster now.
Although this Public Beta of MacFamilyTree 5.5 has been submitted to heavy internal testing, crashes and even the loss of data cannot be completely ruled out. Please make a backup of your family tree before upgrading to MacFamilyTree 5.5.
Download MacFamilyTree 5.5 Public Beta at http://www.synium.de/products/macfamilytree and check out the new features.