Apple today released iTunes 11 for Mac and Windows users. Originally announced in September, with an expected October launch date, its release was delayed until today.
Courtesy of Apple
iTunes 11 is the first really major release of iTunes in some time. It includes a new user interface, new organization, and better performance. It's also tightly integrated with the iCloud and iTunes Match services.
Any major rewrite of an app raises a lot of questions about how well it will perform, what new features it offers, and whether the new interface is any good.
After downloading iTunes 11, I'm on the fence when it comes to the interface. The sidebar is mostly gone, although it sometimes makes an appearance, in new dress, depending on what view you're using when looking at your music library.
The mini player, which I use a lot, is now smaller. That's good, but it's not as well crafted as the one from previous versions of iTunes.
All in all, I have mixed feelings on iTunes 11.

You can change the view to show side bar if you want. Probably best to learn how to use software before reviewing,
You can show the sidebar by pressing Option-Command-S on a Mac or Control-S on Windows. Alternatively, you can open the View option from the menu bar and select Show sidebar.
my main problem with the new update is i cant seem to find the display duplicates option so until thats easier to find 1 star out of 5
Probably best to read and understand a post before commenting.
Of course you can show the sidebar by pressing the right key combination or making a menu selection. THE POINT IS Apple changed the default view for no good reason.
Change for the sake of change is stupid. Taking a step backward in terms of usability is stupid. When you make changes in software, the goal is to make it better. Squash bugs, add new features, improve existing ones, improve performance, and eliminate what doesn’t work or work well. iTunes 11 is definitely a mixed bag.