Yeah if it's pretty much the same, then I don't really care to change. I'm used to screen and happy with its functionality. Vertical splits aren't game-changing enough for me to learn a whole new app.
I love tmux, but it's crazy that they went to all the trouble of rebuilding screen without fixing one of the most glaring flaws to a newcomer: the guaranteed-to-conflict default key binding.
(this makes sense if you use Ctrl-A as 'Home')
Also: http://tmux.svn.sourceforge.net/viewvc/tmux/trunk/FAQ