iTunes 11 introduces a significantly new user interface design, with the long-standing left sidebar essentially replaced by a set of drop-down menus. If you’re more comfortable with the classic sidebar, however, the good news is that you can very easily turn it back on simply by going to the View menu and choosing the Show Sidebar option.
This returns you to a somewhat more traditional iTunes interface, along with the added bonus that the colourful pre-iTunes 10 icons have returned.
Note that the UI in this mode is actually a hybrid of the standard iTunes sidebar with the newer iTunes 11 layouts in the main panel, so you won’t get everything back from the classic interface, but it should definitely be a big help for experienced users having difficulty finding their way around the new version. Note that the status bar can also be toggled back on from the View menu if you’re wondering what’s happened to the totals previously found at the bottom of each screen.