WriteWay Pro has been going for years, in all fairness, and does indeed predate Scrivener by several years. It was one of the pieces of software I tried when I was back on Windows, looking for my perfect writing software, before I decided to write my own (by which time I'd moved to a Mac).
The original idea for Scrivener came from me wanting to combine Windows Explorer with Word (sort of) - have a navigation pane on the left that would allow me to switch between all my snippets without having to change programs and have multiple windows open (I also wanted a split view and some way of connecting synopses with each snippet, so that I didn't have to keep a separate Excel file of summaries of my Word docs...). Before writing Scriv, I tried out all the existing software, thinking that there must be something that did that already - nothing did; there was already a fair bit of writing software out there that had a navigation pane and text view, but none had the flexibility I wanted (it was a screenshot of NewNovelist in a magazine that really gave me the idea that it was possible to have navigation and editing in one program, and I was bitterly disappointed when I bought it and realised that you couldn't navigate at all, only fill in the twelve-step hero's journey of Christopher Vogler).
WriteWay Pro was one piece of software I evaluated on my quest - along with another, similar piece of software with "Write" in the name that I forget the name of (WriteItNow! That was it), but it forced you into working with Acts, Chapters and Scenes, and had a very rigid three-act structure, at the time, I believe. I didn't want that rigidness; I wanted complete freedom to structure everything exactly as I wanted. I don't know if that's changed in WriteWayPro since, or if there was always some way around it, but as I recall, that is the main thing that put me off. It seemed a decent enough piece of software on its own terms, though. (RoughDraft was probably my favourite of the bunch, which is sadly now defunct - the trouble with that, though, was that its navigation pane really was just a window on Windows Explorer, so your files were still all separate and you could only sort things alphabetically and suchlike, I think - I may be wrong as it's been a long time since I evaluated all of this software. That allowed you to switch between scriptwriting and normal text modes, too, long before Scriv came along.)
I do note, however, that there seem to be several pieces of writing software sponsoring NaNo this year, so we have more competition than usual! Still, while that might not be so great for us and our plans for world domination, it can only be a good thing that the participants have so many options.
Although I do see that one of the sponsors claims that their software eschews "tired" "caulk pinboard" metaphors - I have yet to see a pinboard made of a silicon sealant, so I don't know what's "tired" about that, I think that would be a rather exciting pinboard. Miaow!
All the best,
P.S. In fact, we even have a link to WriteWay Pro on our links page