Configuring tmux is easier than configuring screen. And you can patch screen to do vertical splits. The patched screen has been the one that installs in Ubuntu for some time now.
For some reason the vertical split patch (available on Macports) stopped working once I upgraded to OSX Lion and I find myself depending on terminal "tabs" to mimic it (which is slow and painful). Well, maybe it's time to make the move to tmux!
