Ever SSH into the same machine twice? Put tmux on your servers. Or use it to leave jobs running and check on them later.
Edit: Almost forgot. If you use a console editor like Vim or Emacs (well, Emacs people probably do this all inside Emacs) you can basically build-your-own IDE by running arbitrary code in tmux panes (again, your imagination is the limit here) or send code to a REPL or...
The other feature that's used often is the general scriptability that the command line options make possible. "send-keys" for example can be useful...it sends keystrokes to specific named sessions.
Without talking about the other huge benefits of tmux, mosh only helps (and was designed to) prevent disconnections and other inconveniences when your internet connection falters. If for example your terminal unexpectedly closes you can't reconnect to your ongoing mosh session (this is an intended feature for security reasons).
Tmux on the other hand wouldn't help against a poor internet connection, but at least if your terminal or your ssh session closes you can just restart another one and wouldn't lose anything.
In other words, always use tmux, and tmux+mosh if your internet connection is poor.
It's also extremely slow. Fullscreen terminals on my 30" display are borderline unusable with mosh.
If you're connected to a remote machine, run 'tmux -CC'. Tmux tabs on the remote machine will appear as iTerm tabs on your local machine. (This works for attaching to existing tmux sessions as well: 'tmux -CC attach'.)
I was told about it by a coworker - more detailed info can be found here:
I also just prefer the interface of tmux. You can completely configure your status bar as well, and I find that really useful. For example, my status bar [1] has my current music, host, time in the two timezones I care about, and load. I also use a commandline chat client for work that I can embed into a tmux pane and never have to switch away from iTerm to communicate.
On another machine, your session remains alive even when you disconnect.
You can get the best of both worlds with iTerm, by running tmux -CC, which shows tmux's seperate tabs as iTerm tabs, which is super-cool when you are connected to a remote machine!