Sometimes the text is really hard to read because it’s placed over something busy - easy to read while typing it, but once you leave the editing, the background is transparent again. (Treating the background to a call-out box as any other texture would be cool)
It would also be nice to be able to move (/re-assign) the pin point of a call-out instead of just being able to move the call-out text. Actually, having snap-to points on the box would be useful too.
Being able to manipulate the “text box” like it’s a surface/shape would be nice: re-shaping it’s boundaries, snapping to other objects, rotating, scaling…
And being able to manipulate the scale/orientation of the content (treating it like an image fill) would allow for proper 3D labeling.
It would be really neat if every call out was a dynamic component that “hid” the text until the marker was clicked on; the text would then show up (if you were being uber cool you could set transition effects for different ways that the text would display) You could even have a tic box for a “half-way” stage that was small - grew on mouse over and restored back to small when clicked on.
It would also be nice to set the orientation of a call-out to be stationary, to always face the user, or to only face the user when clicked on/mouse over/ button hold/whatever.