Performance improvement goals are to reduce full import timefrom 2 weeks down to 60 hours for very large directories (i.e.200K users, 600K groups)
Recent anecdotal evidence: 300K users, less than 7 hours for full import
Some of those improvements included:
Adding indexes to certain user properties that eliminated full table scans
Importing data from BDC in batches rather than one by one
Removing unused provisioning steps
Cleaning up unused historical data
Move resolution of some objects out of SharePoint and into the sync system