So you can have a headless box or dedicated server running tmux. In the session is your development work, irssi irc clients, documents you frequently edit. They can run for months or years. You could be on your laptop or system at work or desktop at home, and you ssh in with xterm/iterm/putty and type 'tmux attach' and you're home again. I made a datacentre trip a few weeks ago and was working on some stuff from a crash-cart monitor to a unix tty. My session came up, I was back home.

If you have iterm, then you're tied to Mac OS X. The developer or Apple can change something (they're prone to doing this) and then you get left in the cold.

Tmux is a different way of looking at the world, that makes the workstation you're running on mostly irrelevant. With the tmux approach your workstation needs become trivial. Do I have ssh? Perhaps - do I have a web browser? OK - go.

The unix toolchain offers an opportunity to learn a complementing set of weird but really powerful tools once, an then iterate. As time goes on you get better and stronger with them, and can ride them forward for your career/life.

The main use case for that in tmux is when you ssh into a server, start tmux and vim, do some work, then log out without shutting down the tmux daemon. You can then log back in the next day, reattach to the tmux daemon, and continue with your tmux layout the way it was when you logged out the previous day.