The point is that you want to have a system that is responsive.
I remember right after Carter got elected, I was sitting in my apartment in Albany, CA, on a Saturday listening to people call Carter and ask stupid questions while I designed the screen editor.
I think it killed the performance on a lot of the systems in the Labs for years because everyone had their own copy of it, but it wasn't being shared, and so they wasted huge amounts of memory back when memory was expensive.
I think the hard thing about all these tools is that it takes a fair amount of effort to become proficient.
The fundamental problem with vi is that it doesn't have a mouse and therefore you've got all these commands.
So Chuck and I looked at that and we hacked on em for a while, and eventually we ripped the stuff out of em and put some of it into what was then called en, which was really ed with some em features.
I think one of the interesting things is that vi is really a mode-based editor.