Odd, I'm using "GNU Emacs 24.0.50.1 (x86_64-apple-darwin10.2.0, NS apple-appkit-1038.25) of 2010-03-27 on gallifrey.local" and it still has the dashes on the modeline.
If you are going to use a prerelease Emacs, you should update it more frequently than every 7 months! (This particular change is from about two weeks ago.)