Creating a TeX file can be a laborious, tedious and frustrating experience. Any tool the eases the process is to be warmly welcomed. Such a tool is TeXnicle.
The interface is clean and uncluttered. One of the chief advantages of this program (for me, at any rate) is the integrated window environment: the TeX file, the console and the preview can be made visible all at the same time as panes in the main window. However, should you choose, It is possible to make any of the panes go away if you wish.
There are palettes that: provide convenient access to a wide range of macros (both character and structural); provide access to currently open documents; and control over running TeX.
A number of 'engines' are provided with the program (pdflatex, xelatex, etc.) though it is relatively simple matter to create your own -- a very basic knowledge of shell scripting will help.
There is a robust mechanism for handling 'projects': multiple TeX files that are a part of a larger work -- chapters of a book, for example.
There is a very extensive set of preferences that allow you to control a wide variety of the program's functionality.
Crucially, the developer is obviously deeply committed to the task of making the software a good as it can possibly be. He is both responsive and thoughtful, open to new ideas and, altogether, a very nice chap.
Though the version I am using (version 2) is currently in beta, it is extremely solid -- I have had no problems at all in that regard.
In short, TeXnicle has become my TeXing environment of choice.