Simplenote was one of the first applications I adopted to keep track of notes from multiple devices. It follows a two pane format: title on the left column, content on the right.
Simplenote doesn't do formatting (although the web version, and some clients do offer markdown and Rich Text). Nonetheless, it does have a full complement of text editing controls, gives me an automatic word count, offers a fast and powerful search function, and presents a clean user interface. I do a lot of writing in it, mostly short pieces, but sometimes as long as a magazine article. While Simplenote doesn't offer outlining, it does have a robust system of tagging. Tagging isn't outlining. But it's handy.
Simplenote is free. It saves its files on its own cloud, which has proved to be reliable, and does an admirable job of syncing quickly and correctly across every platform I use. (It also has some popular variants on the desktop: Notational Velocity and nValt for the Mac, Resophnotes for Windows, and nvpy for Linux, among others.)