Can you please expand on what :open does and what it's useful for? :help :open tells me nothing at all :-(
Open-mode is a quasi-Ex and quasi-Vi mode, or could also be described as "Vi mode on a glass/printing TTY". It doesn't redraw the screen. I found it useful when I had to use a printer as my output device: it offered the power of vi, but with the terminal-indifference of ed/ex. It's also helpful for doing what you describe, of having some of your shell session (prior to vi/ex invocation) available on the screen at the same time, yet still have the ability to navigate like in Vi.
I believe both the "nvi" and "stevie" clones both implement open mode.
-tim
