emerge just updated tmux to 1.3 for me. After I restarted tmux (actually, a crash helped me to restart my system, what a coincide), few warning about down-pane and up-pane command is not recognized. That is actually warned by emerge already:

>>> Messages generated by process 9991 on 2010-09-07 20:52:34 CST for package app-misc/tmux-1.3:

WARN: setup

Commands 'up-pane', 'down-pane' and 'select-prompt' were removed in version 1.3.
You may want to update your configuration file accordingly to avoid errors on
tmux startup.

For the full 1.3 Changelog, together with details on what replaced the above
commands, visit http://tmux.cvs.sourceforge.net/viewvc/tmux/tmux/CHANGES.

WARNING: after updating to tmux 1.3 you will _not_ be able to connect to any
running 1.2 tmux server instances. You'll have to use an existing client to
end your old sessions or kill the old server instances. Otherwise you'll have
to temporarily downgrade to tmux 1.2 to access them.

As I said, my system crash, so I didn't get that message at first. I read the man page and that changelog and resolved the issue by myself.

The screen is actually cleaner:


The current pane indication is used to have white line on green. Now it's a simple and clean green line.

There is also a change, it now seems to shows current pane's window (not the window in tmux) name in statusline if window name gets updated.

I did update for sudo originally for the security issue about privilege escalation.