I referred to a review of Scrivener in the Chronicle of Higher Education earlier. They have just published a review of an application, called "Writer's Cafe", which is available for both Windows and the Mac. (It's also available for Linux.) The review is on the whole positive. The reviewer finds, for instance, "Writer's Cafe is intended as a fiction writing tool, but you can also use it for other types of writing. Indeed, the naming convention used throughout the program refers to storytelling: storylines, screenplay formatting, character development, and there's even a "name generator" for characters. If you can move past these conventions, Writer's Cafe becomes useful for project-based writing."
I have never been able to get past the naming conventions (and I do not understand why they are hard-coded into the program). Even the name is overly pretentious (if that isn't a pleonasm). As a result, I have never given this program a thorough trial.
I have seriously tried yWriter which is less visual but otherwise quite similar, and the "fiction metaphor" drove me bonkers. I don't want to create the (slightest) appearance of writing a novel—even to myself. So I will stick with ConnectedText as my Scrivener for Windows. It's much less pretentious and much more flexible.