it is lightweight, contained, and excellent if you have a "unix-like" workflow. Typically I'll have a watch script, server, and vim in a given window, and it is super compact. Some cons are probably the learning curve required to see any advantage, and the fundamental lack of any respect for mousing, which can be in the pro column for many.
That's interesting. I practically never use the mouse to switch between windows in OS X or Windows.
The biggest problem I have with tmux is vertical splits don't work with native copy-paste because the selection goes across both panes. Using multiple terminal windows, on the other hand, doesn't have that issue.
Using a mouse, you can use tmux's new (in 1.8) pane expansion. prefix + z causes the current pane to take up the entire window. prefix + z again and it goes back to normal. Essentially, it's a maximized/restore capability.
