There is an easy way to set up a LaTeX system on OS X, of course. I just don't think it's so much fun to use, at the moment:
That's it. If you want an even simpler LaTeX editor, without the automated macros and typesetting commands, you can use SubEthaEdit (itself a wonderful code editor with line numbering and syntax colouring) or iStorm (which includes the BabyTeX module that provides templates for LaTeX formatting and equations). Both of these have the ability to edit documents collaboratively over a network.
The only WYSIWYG TeX editor I've managed to find is TeXmacs, which runs under X11. It's surprisingly smart, but uses it's own formatting language (though can import and export LaTeX and uses the standard tools to produce PDF output).