One other thing I've encountered:

 I can now run ardour after starting jack with qjackctl, but if I start Ardour first, and go to the 'audio setup' tab and select 'FFADO', then the interface box is empty, as well as the 'input interface' and 'output interface' boxes on the 'advanced' tab.  The pulldowns give me no options, either.  I don't see anything like this reported as a bug on the Ardour tracker.  I wonder if it's still an anomaly in my config?  I do see the same mis-behaviour on both my US10.04 and FC12/CCRMA test systems.