The main advantages of LaTeX are (especially for mathematicians):
- semantic markup
- high typographic quality (among others of mathematical formulae)
- availability (and price)
- extensibility
- being a de facto standard in mathematical publishing
There are, however, some disadvantages:
- a bit steep learning curve
- customizing (almost) everything is possible, but for many things it is not easy
- conversion from and to other formats may be a bit tricky