What's missing
cat TODO
Currently here are some features that screen has and tmux does not:
Searching through the copy-buffer: Nicholas is on it
Logging a window to a file: [can be done using script(1)]
Support for serial terminals: use cu(1)/tip(1)
Wider platform support (HP/UX, Irix): in progress
Better terminal support: in progress
Cannot be shell yet: in progress
Cannot use system password for unlock: ?
Cannot rebind mode keys: ?
No utmp updating: probably will not be implemented