yuck. . .
Maybe I shouldn't be surprised that Ubuntu and Fedora are doing that, but I am. Someone please correct me if I'm wrong, but my impression is that Ext2 remains the best bet for Linux filesystems, unless you have a real need for filesystem performance. Ext2 is stable and well tested, and linux has plenty of recovery tools for it. Even other mature filesystems like xfs, reiser, and jfs seem to lack the same support on Linux.
If you run into a strong need, you can always upgrade ext2 to ext3 or ext4, but I don't think you can go backwards. Given Ubuntu's target demographic, do the performance benefits of ext4 really outweigh the risks, or is this just a case of some hacker geeks who are happy to have the latest and greatest on their own machines sharing the joy with everyone else? As I get old and boring, I increasingly lean towards avoiding unnecessary risk.