You can make the new iTunes look and feel much like v10 by using the following short cuts:
ALT shows the menu bar temorarily
CTRL+B show/hide menu bar
CTRL+S show/hide side bar
CTRL+/ show/hide status bar
To make search more like it was, click on magnifying glass in search bar and uncheck "search entire library"
If you sitll want to go back you cna download the old iTunes here:
Uninstall iTunes and install the old iTunes.
You will need to recover the backup library made when you upgraded, see