A release candidate has now been tagged in SVN as 1.2.4rc1. You can either grab it through svn at http://svns.automattic.com/wordpress-mu/tags/1.2.4rc1 or download a zip file at http://trac.mu.wordpress.org/browser/tags/1.2.4rc1
If there are no major problems (beyond the ones already reported in Trac) I'll release 1.2.4 tomorrow.
Thanks for all the bug reports, and patches!
Donncha.