MPW's unification of a command shell and an edit window took a little getting used to, but it was really, really useful once you learned the single trick. (Not to keep you in suspense: the ENTER key just inserted a newline, while COMMAND+ENTER executed the current line, or whatever was currently selected).

To this day I miss this ability on command shells. On Windows there is lame cut-and-paste (and it's disabled by default). It feels like cement galoshes, all that dead text just sitting there on the screen, useless and flat.

Never used MPW nor seen it in action, but many people have told me there are similarities. Being able to type stuff and double-click on it, I think.

I'm working on making a page that highlights similarities between Xiki and various tools / paradigms.

One neat feature: you could specify regions of a window (text document) as a separate file, so you could perform redirections to and from. Of the window was "Fred" you could, eg:

Echo "main() {}" > {Fred}.$ cc -o mything {Fred}.$

(Of note, the actual syntax included high bit MacRoman characters, so you were actually using the "section" glyph rather than $)