I have been using GNOME 40 for months now. I barely notice any difference with GNOME 3.38, except for the position of “Activities” icons (no more on the left side, but on the bottom side of the screen).
One of the things I love the most about GNOME is that you rarely need to use the mouse. Most actions are performed via keyboard and every time I need to go back to Microsoft Windows it is really a pain to have to use the mouse again for the basic things. Nothing substantial has changed in that respect with GNOME 40.
@amarok I would also be curious to know the answer to this question.