10.2.2 is out and it has journalling available as a Disk Utility option for OSX Server. The option is still there for OS X Client, but hidden.
Journaling allow the system to recover more easily from crashes and protect against corruption by having a "journal" (a buffer where changes are first made and then afterwards written to disk) and makes recoveries much faster when using tools like fsck. In exchange for this, extreme disk usage could have an impact (up to 10%) on performance. So, it's not recommended if your machine moves a lot of files around unless it's a file server, in which case it is *strongly* recommended (the priority in servers is safety of the files, not the speed of the disk).
To enable journaling on OS X Client, use the Terminal command:
% sudo diskutil enableJournal /There does not appear to be a man page, but 'diskutil --help' will get a rudimentary list of commands.
Mac OS X Hints
http://hints.macworld.com/article.php?story=2002111200220086