Rails currently doesn't support the dirty methods for an attribute alias's.
i.e. if you setup an alias called title (alias_attribute :title, :name) then title_changed? isn't defined.
Rich has written a simple patch so the dirty methods are defined for attribute alias's -> http://rails.lighthouseapp.com/projects/8994-ruby-on-rails/tickets/812
Please +1 it if you'd find it useful.