I use articles out of box, but my article forums are pretty basic, short-run, themed (e.g. one member shared draft chapters of a book they are working on). And it works fine for that.
But, yeah, when I was looking at taking over the writing site where I publish my writing, I was definitely talking to Bob. It had basically all the features the writing site needed. Never happened as the owner went a different route, but it gave me a chance to look at AMS. Very good product if your focus is writing of any kind (articles, stories, etc.) And as long as it exists, not sure Xenforo should be putting in the effort. I can't see how they could do better short of making a first-party add-on for articles. Which means you still have to pay extra for it.