For those unfamiliar, LaTeX is a very flexible typesetting language that allows full control of anything from simple formatting to the proper display of complex formulas.
See http://en.wikipedia.org/wiki/LaTeX and http://www.latex-project.org/

I think adding the ability to parse and display LaTeX code could greatly enhance functionality without really increasing complexity of the user interface. This is a great program to store and represent just about any idea that can easily be expressed in text. I am however, sorely missing two features:
-The ability to input cleanly formatted formulas.
-The ability quickly draw small pictures/graphs/schematics withing the program to add them directly into the thought structure.

Providing functionality in this regard would probably help quite a few people from engineering/science/math fields. Extending at least the text formatting options through LaTeX (or something similar) would probably help more than just people from those fields.