I edit a lot of plain text in the course of my work: source code, HTML, etc. I also regularly use regular expressions to massage plain text and HTML into shape, search/replace, etc. And sometimes dealing with Microsoft Excel, Apple Mail or other programs demands converting to plain text in a way those programs can’t handle. And then there is high speed performance both while editing and for search and replace stuff.
Thus a good plain text editor is essential for what I do.
My plain-text editor of choice is BBEdit. They are among my most-used tools, every day, day in and day out. Both have a free 30 day trial. And for real geeks, they even have optional command line tools in addition to the superbly useful app.