> You write a really long document using one citation and formating style, and then you find out the journal requires a completely different style. ... If you are changing to a known style such as IEEE for example you can simply download appropriate templates, toss them to your project directory and add one or two lines to your document.

It's another question entirely if you have to create your own style.

This is one point where Word wins, but it's a big one. The learning curve for LaTeX is already pretty steep, but it goes vertical once you start to mess with layout. It works in academia and publishing because there are a relatively limited number of templates everyone conforms to that are written by LaTeX gurus.