[St-Clock]

I also use C-s on my local machine because:

1. I can still use C-a with readline (go to first character)

2. If I ssh and then use screen, I can use C-a to navigate my remote screen and C-s to navigate my local tmux.

3. C-s is closer to C-a then other letters on my keyboard.

[e3b0c]

C-a still works with readline. You just need to C-a first to 'escape' tmux and then C-a again. Actually just hold ctrl and hit 'a' twice.

C-s will suspend the terminal on some platforms. (Which can be resumed by C-q.)