If you like tmux and it works for you, great! The last time I played with tmux, it couldn't do all the things that I use in screen. In addition to the usual multiple-pty-management, I also like the fact that screen gives digraphs for extended UTF-8 character input, can connect directly to serial ports (i.e. act as a serial terminal), and remap codepages on the fly (I've still got that CP 437 serial terminal).
