iterm has special integration with tmux.
The big advantage is that you can quickly scroll the history with the mouse which is way faster and more convenient that going back up screen by screen with a shortcut.
Also with some work you can synchronize the OSX clipboard with tmux's one.
Out of curiosity iTerm or iTerm2? If the latter what is crap about it?
I have one huge gripe that I haven't been able to fix but its not that huge a deal. Every so often the terminal will lose its mind and start displaying mouse escape sequences. Nothing resets it out of this state, have to close whatever window I have open and start anew. Not a huge deal due to tmux but annoying enough to frustrate.
> The big advantage is that you can quickly scroll the history with the mouse...
I've not found that to be faster than <CTRL+F> or <CTRL+B>. Same keys as in vim. I haven't found the value in using iTerm over terminal + tmux (same could be said for those that are more comfortable in screen).
Also with some work you can synchronize the OSX clipboard with tmux's one.