Tmux/Screen provides an extra redirectable abstraction layer over the terminal device.
The biggest complaint I regularly see about it is that people are used to the screen keybindings. I wonder why not add an abstraction layer there, where keypresses really call commands that perform the actions, and you could reconfigure these.
This is how Emacs has done it for 30 years...
That's my problem with Tmux. Ctrl-a,d is already burned into muscle memory, and for my applications Screen is "good enough".
2. in the first shell you get run:
tmux set-option prefix C-a
Permanentize it by changing tmux.conf :)
https://github.com/tmux/tmux/commit/2a1bb9#diff-fefa423d67264099ae82d4d2f5422b09
set -g prefix C-a
unbind C-b
bind C-a send-prefix[1] that is, using the Emacs keybindings it exposes by default. I know you can change that through .inputrc