A bit off topic, but if some OS X users need a
mouse only for Acme, here is a patch to use Acme
without a mouse:

          http://codereview.appspot.com/6115053

Once applied, Devdraw's manual (accessible from
the Help menu) will show the following:

          On Mac OS X 10.6 or later, the following gestures are avail-
          able for trackpad users:

               2-finger-pinch to toggle fullscreen,
               3-finger-swipe left to cut (cmd+x),
               3-finger-swipe right to paste (cmd+v),
               3-finger-swipe up to copy (cmd+c),
               3-finger-swipe down to exec with arg (2-1 chord),
               3-finger-tap to middle-click.

          (Equivalent 2-finger swipe gestures are available for Magic
          Mouse users.)

          Swipe gestures will only be available if the system does not
          use them.  On OS X 10.7 for example, the default trackpad
          configuration must be changed as follows:

               swipe between pages with "2 or 3 fingers",
               swipe up to Mission Control with 4 fingers.

I use this patch since many months, and I find
Acme even more fun than before. You can apply the
patch this way:

          hget http://codereview.appspot.com/download/issue6115053_1.diff >
$HOME/Downloads/swipe.diff
          hg -R $PLAN9  import --no-commit $HOME/Downloads/swipe.diff
          cd $PLAN9/src/cmd/acme && mk install
          cd $PLAN9/src/cmd/devdraw && mk install

If this patch conflicts with "hg pull -u" one day,
you will just have to run the following, to trash
all local changes:

          hg -R $PLAN9 update -C

and apply an updated version of the patch.

This patch, that is just a hack, has been refused
at least for the following reasons: it is too
Acme-specific; it can require change to OS X
default conf.