I think Textile is the most natural and intuitive way to format text. When I first brought it into this site, it only took a couple of hours to get used to it. And now, apparently I write it without knowing.
I had to submit a Power Point last night for a presentation I have to give in one of my classes, and I just now glanced through it again before wiping it from the task bar—what do you think I found? Not one, but two places where I threw in some Textile underscores. I guess I was thinking “File > Save” meant “Submit” and the text would magically convert itself into italics. But it didn’t. Though I do wish I could use it on desktop text processing.