I like to compose my equations in LaTeX. I find it a lot faster than the click interface of MS Word's own equation editor. I type up my notes in a LaTeX format so I already have the equations and its a terrible inefficient duplication of work to hunt-n-click them into ms word.
One solution is to print a pdf of all the equations, and then use the select tool in preview to copy the equation and then paste it into the word document.
The advantage in mac os x is that the copy is in vector format, which means that the inserted equation does not behave as an image - becoming pixellated at the worst moments, but rather scales gracefully.
That's gonna save me some time.