You get the new user interface if the menu bar is hidden. To do that in the View menu select Toolbars, then click on the "Menu Bar" entry.

Thank you TonyE. You solved my problem.

The 'new' user interface involves clicking on more buttons to get the same result. So it is a time waster and time costs money so the saying goes. One click to get the menu that used to be visible anyway.

New Version: 'Firefox' and then 'Options' to see the Toolbar list. This is illogical, it might still be two moves but who would have expected to find Toolbars under Options!

Old version : 'View' then 'Toolbars' and you see all your toolbar options. Simple and intuitive - a sign of good development that firefox 4 has ignored.

And where has the 'Import' button gone? What has it been replaced with?

Not defending the idea but like dropping the Status Bar, hiding the Menu Bar is all about saving space. "Import" is in the File Menu in the hidden Menu Bar where it always was or in Firefox Button>Bookmarks>Show All Bookmarks>Import and Backup.

All you need to do is to hit the Alt key to temporarily reveal the hidden Menu Bar to be able to access those menu items - File, Edit, View, etc.

And being able to "hide" the Menu Bar isn't new to Firefox 4.0/5.0, Firefox 3.6 had that same feature as an option, but without the orange (or grey on Linux) Firefox button. IE8/9 has a similar feature that allows you to hide the Menu Bar, and it works the same as with Firefox 3.6+, where the Alt reveals the Menu Bar for access. Plus Opera 10.0+ versions work pretty much the same, when the "Opera button" is set to show, hitting the Alt key shows a drop-down menu that replaces the Menu Bar item for item.

Just a matter of the user educating himself or asking questions when they see a new feature in any software they are using, instead of dismissing the new features as "time or money wasters".