Storyspace for MacOS X
It is software that I am very fond of. I find it very easy to write in, much easier than Tinderbox (which I tend to use to collect information in, but not for writing longer pieces). I’m looking forward to getting this, and once again writing hypertext, hypertextually. (That is, writing in a purely hypertext environment where my practice is concerned with writing, and writing as hypertext. Design, which is what happens when I write in html, can come later. In Storyspace things get pared down, words, links, nodes, link structures, maps.)
It's interesting that Miles finds it easier to write in Storyspace than Tinderbox; my impression is that, for the process of composing, Storyspace and Tinderbox are very similar. They share the same text engine, for example, and Tinderbox and Storyspace map views are equally expressive.
Tinderbox does give you more export options, though, and the presence of those export options might in fact be a hurdle. Knowing that you might be destined for HTML can lead to to start working on graphic design too early, before you really get down to writing, perhaps before you're certain that there's something to be written. More than once, I've been left with a nice design for a project that didn't pan out.
But perhaps I misunderstand Miles's issue.