Hi, say I have a User model with an active observer:

class UserObserver < Mongoid::Observer
def after_update(user)
Rails.logger.info(">> #

")

when I update a user:

ruby-1.9.2-p180 :005 > u01.name = 'ABCDEF'
=> "ABCDEF"
ruby-1.9.2-p180 :006 > u01.save
=> true

Then Rails loggs only '>>', so the previous_changes hash doesn't make it through to the observer.
This happens at least in commit 26dec02b1.
--Frank