It is thoroughly scriptable, including working with Automator. It lets you see an manipulate all your text formatting. It is the boss of UNIX and DOS formatted text, allowing you to do anything you wish with it. It allows integration of audio, graphic and video into your files. It is THE BEST text-to-speech reader available, bar none. Then consider the terrific raft of features in Tex-Edit Plus X that reside under the hood. When I write I just want to write without any distractions from my text editor. I write just about everything in Tex-Edit Plus X, then toss the text into a more powerful manager or page layout program for my finished product. It is intuitive, powerful and just works, all without clutter and crud getting in the way. It is actually a relief to be able to use Tex-Edit Plus X after contending with the multitude of alternatives. Tom Bender, the developer, has thankfully put hard work into version 4.9.9 such that it is again my favorite and most used text editor.
While using Mac OS X 10.6, I was a bit displeased with problems in version 4.9.8 and thoroughly dismayed that it no longer worked in Mac OS X 10.7 Lion.
It has been my pleasure to own and use Tex-Edit and its descendants from ages past through today.