In the line of tabs along the top of the screen, there used to be an extra tab with a + in it that you clicked to open a new tab, on the right hand end of the tabs. As the tabs always float left and new tabs appear on the right this was (in my opinion) the most logical place for it. However, now the only two places I am able to put this "tab" are at the extreme left, which is illogical seeing as the new tab appears on the right, or in the toolbar along with other tools. This is adequate, but I would prefer to see the "new tab" tab back where it was.

The option to put it on the far right of the tab ribbon was not working until this latest version of Firefox, by the way, but I'm sure you know this!