TextExpander’s capability to substitute a simple text string on the fly for something that you type is well worth the price of admission. But TextExpander snippets can contain more than just simple text, and they can do some cool things.
You can create snippets that include formatted text and images. Moreover, using TextExpander macros, you can make snippets that include clipboard content, move your cursor, and type special keys like Escape and Tab. Snippets can even perform date and time math, combine several snippets into one, and generate fill-in forms.
“Complex,” however, does not mean “hard”—complex snippets are easy to create and easy to use.
And the uses, as you might imagine, are plentiful.