Most people I know use it to go to the beginning of a line in programs that use readline, which includes the shell as well as most programming language interpreters.

You can set readline's editing mode to vi so that anything that uses readline will then have vi-style bindings. Very useful, particularly when combined with rlwrap for those few programs that don't have readline support.

Zsh doesn't use readline (it has it's own line editor) but it can be set to vi-style input too. (Actually, at least on my system, bash doesn't seem to be linked with libreadline.. I'm not sure if it is actually using readline or not)

Bash uses .inputrc which configures readline, so if it's not actually using libreadline, it's emulating it pretty well.

It looks like bash does use readline, though it's not dynamically linked with it (at least on my system). Kind of seems like bash and readline are intertwined more than I thought; the git repo for bash has a distribution of readline included in it.

That makes sense to me. The shell is fundamental to the system, and is so heavily intertwined with readline that it is very sensitive to ABI/API changes. Consider: if you upgrade your readline without upgrading bash, or vice versa, you lose the ability to fix the problem even in single user mode. Having Bash control its own readline usage seems like the safest option, though conceptually a bit more complex.

I started using screen before I started learning that facility. (At the time, I mostly used Windows, so the Home key was available.)

Of course, when I started developing on a Macbook, screen rapidly became problematic as there was no Home key and I started using Ctrl-A. For the moment, I'm developing locally so I don't need screen or tmux, but I'm working on off-loading to a VM and I'll be using tmux there for the purposes of maintaining my own sanity.

I map Ctrl-q to beginning of line in .inputrc.

    Control-q: beginning-of-line

I know, I know, now we are remapping all over the place. But my muscle memory for Ctrl-a was too ingrained after years of screen usage.

With a vimscript [0], ctrl-a can increment dates, times, roman numerals, ordinals, etc. Pretty damn handy along with ctrl-x to decrement.

[0] https://github.com/tpope/vim-speeddating

I actually do use that, but ctrl-a/ctrl-x is still something I rarely find myself using more than a few times a week. Still a great plugin though.