1. We need to clearly separate the difference between UI design and UI decoration. Design should be driven by user testing that measures speed and rate of completion of tasks. If every feature of the latest UI is not measured to be a quantitative increase, then it is not a design improvement. Decoration is about being fashionable and has nothing to do with usable, efficient, elegant UI. I see no reason they cannot exist side by side, but today the prevailing policy seems to be that decorating UI in a trendy fashion trumps usability.
2. There needs to be thought about the adoption and transition of users from an old interface to a new one. Right now the philosophy seems to be "Stop whining and suck it up - our designers are smarter than you." This is not reasonable or professional. New designs should be measured not just for usability of new users, but also against users that are used to the previous interface. There are probably many techniques to improve the user experience of UI upgrades but we'll never discover them until we recognize that it is important and spend some time and effort studying this phenomenon.