Windows/Mac/Linux: Atom, GitHub's free text editor, has been toiling away in beta builds for a while now. Today, it's officially available as a stable version.
Atom is still open source and still cross platform, but now comes packed with a pretty solid feature-set alongside improved stability. The appeal of Atom is its modularity, which is a fancy way of saying you can customise the editor in all kinds of ways to suit your needs. As you'd expect with the stable launch of an open source project, the update list is pretty massive, but the big improvements include pan resizing and multi-folder projects. You can find a full list over on the Atom site.