I use LaTeX almost every day, and I have lived with it since 1990-91. The elegance that you get, the control you have of the layout, and the ease in doing something new by taking something old (like a table) and modifying it to render a perfect, new structure, is immediate. The fact that the handling of equations, tables - as mentioned - and the ease of fixing the reference list through BibTeX is yet another winning argument. There is not one competitor with LaTeX if you want to write complex math easily.
Word stands no chance against the LaTeX monster - also because journals in math - which is my field - needs those symbols, that Word simply cannot provide with the same ease and elegance ...