Here's the caveat: it does take a bit of effort to learn. It has a bit more in common with writing computer programs than it does with MS Word, for example. If you've ever edited html code, it's sort of like that. But the effort is time well spent. Here are the main things I like about using LaTeX.
1. Good bibliography management with BibDesk, and automatic citations and bibliography generation. I like this system better than EndNote because it's free, and it doesn't crash or do unspeakable secret things to your document.
2. Ever tried to get a figure in the right place in Word? This process makes me want to stick flaming skewers in my eye. With LaTeX, you put a reference to a figure in the document, and the program figures out a logical place to put it.
3. Equations. Word's equation editor has gotten better, and LaTeX requires some learning of syntax, but once you get it, it works beautifully. All of my math geek friends use LaTeX all the time.
4. Readability. LaTeX documents are easier to read than Word documents.
5. Integration with r through sweave. You can even make documents where figures and results are generated on the fly from your data when the file is processed - so if your data changes, the paper is updated automatically.
5. Reign over other dorks. Being good at LaTeX is the computer equivalent of wearing a Tron costume and speaking klingon (the warriors tongue). AT THE SAME TIME.