My very first software-related blog post was about Grandview. If you're interested, you can find it here:

https://welcometosherwood.wordpress.com/2009/10/10/grandview/

It was the combination of features that was so remarkable. Especially for the time (1989 or there about - when the application came out. My blog post was from 2009). But the best feature was how you could have a full-blown word processor document attached to any node in the outline, and you could view it in its own editor window, or as part of the outline. You can see examples of what I'm talking about in the post.