By the way, here is a free program from the makers of MathType:
http://www.dessci.com/en/products/texaide/
"Design Science TeXaide™ is a special version of our Equation Editor that generates TeX and LaTeX using MathType's translator technology. Whereas Equation Editor can be used with any application that supports OLE or can paste a graphic from the clipboard, TeXaide only generates TeX/LaTeX on the clipboard, where it can be pasted into any TeX/LaTeX system."
Certainly, a more natural interface would use handwriting recognition:
http://www.ai.mit.edu/projects/natural-log/demo/
http://www.inftyproject.org/en/download.html (InftyEditor has a crude live handwritingRecognition-to-LaTeX.)
http://www.microsoft.com/windowsxp/downloads/tabletpc/educationpack/overview4.mspx (renders handwriting to a bitmap...but seems like it's only a step away from an Equation Editor object or LaTeX).
http://www.xthink.com/MathJournal2.html was supposed to have handwriting-to-LaTeX recognition... but I don't think that happened.
..at another level, I'd love to see a scanned-handwriting-to-LaTeX conversion. InftyReader can do scanned-typeset-equations-to-LaTeX. If one is able to convert to LaTeX, it seems like it shouldn't be too much more trouble to convert to [say] Maple or Mathematica.
By the way, at least since Word97, there has always been an Equation Editor, which is not installed by default.