This morning, several testers are reporting that Messenger auto-update has upgraded their version of the Messenger Beta client to build 369. Although we are unable to obtain the upgrade via this method, it appears as though the new build is mainly bug fixes.
You can find the seemingly obligatory "About" menu here.
Update: This appears to be only available for French testers at the moment, via http://g.msn.com/1csbeta/Mess80_FR. We'll let you know when its available to all.