No promises, but I might get around to it this weekend. I've been meaning to write something for a while. The tmux man page is quite thorough, but there are a few things that might be confusing if you expect it to behave like screen, such as layouts.

It's easy... rather than the Ctrl+A key sequence that you use in screen, use Ctrl+B in tmux. And to reattach, rather than screen -r, tmux attach does the trick. That's 90% of the usability difference.