Yep MacOS only for now. SSH works ok, it wraps the native SSH and does some magic so your milage will vary. For TMUX, don't know what you would need that for honestly.
It's super useful for doing things on remote servers. Tmux can maintain a "session" between ssh connections. So I can start a long running process on a tmux pane and then log out and come back to it later to see how things went. I also generally do development over SSH so it's nice to not have to re-set things up each time I SSH into the VM.