[bstar77]

I've been using vim for 7 years and I've never even attempted to use this mode. Am I missing out?

[krick]

Usually not, but over 7 years it's quite probable that there was a couple of times when it would be useful. It's good for batch processing (maybe over several files) using usual vim commands. Something like awk embedded in vim.

[peterevans]

You might be, if you write plugins for vim! But if you don't, then no, probably not. It's handy to test some arbitrary commands which might go into a vim script or, more likely for the average user of vim, your .vimrc file.

[rkowalick]

It seems like a very good way of using vim knowledge to do non-interactive text processing. You could say, indent a javascript file that is ugly.

[tyler_ball]

easier than hitting gg=G ?

[kevinmgranger]

non-interactive