I like this plugin. I've been using WordPress SEO (Yoast) since January. That plugin gives focus word suggestions, but it usually gives dozens (hundreds?), and there's no way to know which are better than others in terms of being found at the engines.
The bizXpress tools (yes, they're not built in to WP, but so what?) give me an indication of what I should be writing first, and what I can expect.
I saw a complaint elsewhere in these forums about this not being a plugin. The moderator told the complainer that it is indeed a valid plugin for software as a service (SaaS).
I'm perfectly happy with that. The entire basis of WordPress SEO is software as a service. So is the Scribe plugin. Neither one's core duties do anything "for" or "to" a site, as the complainer was complaining about. The core of each deals with the content, not with the site. It's only the little addons, such as breadcrumbs and Open Graph tags (both in WordPress SEO) that do anything "for" a site.
Would it be better if the brainstorming tool was built in? Sure. But should I stop using it because I have to go off my site to use it? A lot of opinions here say I should.
Will I stop using it? Definitely not. I'm not going to stop using a valuable tool just because it's not perfect. And most definitely not because others have a low opinion of it.