I first noticed the difference in the navigation pane between version 3.0 and 4.0 since I’m watching training videos which were recorded in version 3.0, but I also wanted to point out that there is quite a difference between the buttons on the screens.
In version 3.0, the buttons were a lot more wordy and they took up more space (sorry for bad resolution, this is a screenshot from a video):
In version 4.0, the buttons take up much less space because the words have been removed. If you forget what a button does, you can hover your mouse over it and the button help will be displayed.