Submitted by “If you have spent enough time around Linux it’s almost certain you know about the file systems ext2 and ext3, and have probably heard of ext4. Get ready to hear some more. On October 11, 2008, the ‘experimental’ label for ext4 was removed. While this doesn’t necessarily mean that you should change all of your file systems over to ext4 immediately, it does mean that you should consider using ext4 moving forward. With the ‘experimental’ label gone and openSUSE (among others) considering it for the default file system in a late-2009 release, it’s a good time to review ext4 so you have a solid working knowledge of what it is and what features it brings to the table.”
I will assume that the author has vetted and/or corrected all those Wikipedia articles he links to, and provides them as an addendum of additional information, not as evidence of the extent of his research.