I find both tmux and Gnu Screen difficult to config (haven't taken the time to learn) but I love the concept of them so I use Byobu (http://byobu.co/) on top of tmux/screen to set common configuration for you. Byobu really lowers the amount of config and barrier to entry because Byobu uses common hotkeys. For example F2 for new window.
Thumbs up for Byobu - a great wrapper that makes using screen or tmux less clunky for me. The default config & hotkeys are intuitive, never had the need to alter them.
I have tried to configure bash for better use it (including launching it automatically) but then gave up due to not enough gain. But I never saw a need to configure tmux itself.
I can't say the same about screen. At a minimum, there's an inherent incompatibility between it and emacs.
The first line sets the prefix key to C-M-6 which is not used by emacs. The second turns off the "ctl-f" flow control stuff so emacs gets that chord. I then use emacs itself for all "window" management and terminal multiplexing.
It seems to me that people tend towards wanting to configure programs like these before they really grok them. Vim is another: I don't think it needs 100 plugins to fulfil its purpose.
I also run screen emacs and urxvt. For what it's worth I choose screen over tmux mostly because I've worked fairly hard at keeping most of my stack gpl.
