Mark Shuttleworth responded to criticism over the changes to the new Lucid window themes with allusion to the fact that new and neat things are coming that justify the change.
Sometimes it’s worthwhile to step outside the envelope and try something new. But always remember that humans respond to risk-reward behavior. If you are going to force them to do something new or risky, there needs to be a reward equal to the risk otherwise the user wont adapt.
In the case of the latest design changes, the reward was promised after the fact, but not given. Thus, it is a massive design fail. Yes there were opinions provided and these can be ignored because of meritocracy rules. But good UI design needs to be based on fact. And the facts were not there to justify the change. This was pointed out. And hopefully completely understood.