If it aint broke, dont fix it!
If it aint broke, dont fix it! Change for changes sake is not progress, it is just job security and egotistical I can make it better or not invented here attitudes.
What was the objective in changing the 11.4 UI. What was the problem with 11.4s UI? Who wrote the requirement description and who reviewed and approved it? Who did a cost benefit analysis for the coding, documentation, testing, and most important, user retraining? What user survey justified this change?
Apple has abandoned its core, experienced, user base. These are not the teenagers, or even the twenty somethings. These are users who have been loyal Apple customers for the past 20 to 30 years and who have made Apple the leading company it is today. Yes, 30 years! I started with the Apple ][c!, the Lisa, and the original 1984 Mac 512. Ive seen the changes in the OS from the beginning. Until Yosemite the OS and UI changes have been logical and evolutionary. Now someone had the brilliant idea to throw out 30 years of improvements and to force users to adopt their personal idea of a UI and to downgrade the Mac UI to a iPhone or iPad level. Why?
Unfortunately Apple has lost its focus on UI just like MicroSoft when it decided to change the UI for its MS Office Suite and impacted millions of users who had invested 10s of millions of manhours in training and learning the UI. An established UI should NOT be changed just because some software engineer thinks his personal way is better. UIs must be undergo an extensive review and approval process BEFORE a single line of code is touched. Then it must be subjected to exhaustive beta testing by real world experienced users across a broad spectrum of applications. AND as a backup there should be an option for a user to invoke the old UI if he finds the new one so counter intuitive that he cant be productive or effective.
And, YES, the sidebar was an effective and efficient way to view and control your iTunes media.