I suspect that these will be as annoying as flashing text, and not immediately useful. Then one has the possibility of getting an overall view of an expression, but being able to click to see more and more details if one is interested. I should have made it clearer that the area I have found graphical notations difficult to handle is in representing traditional mathematical actions and operations. In my new science I use graphics all the time, and I cannot imagine doing what I do any other way. And in traditional science and mathematics there are certainly graphical notations that work just fine, though typically for fairly static constructs.
Graph theory is an obvious place where graphical representations are used.
Related to this are, for example, chemical structure diagrams in chemistry and Feynman diagrams in physics. All of these notations, however, become quite obscure if one has to use them in cases that are too big. But in Feynman diagrams, two loops are the most that are routinely considered, and five loops is the maximum for which explicit general computations have ever been done. In Mathematica 3 we went to a lot of trouble to develop fonts for over 1100 characters of relevance to mathematical and technical notation. In the end, I actually drew sketches for most the characters.