Comment 4 for bug 823971

nilfs2 is unstable (see the big capitalized warning in dmesg if you load the module), it is in flux and there is no guarantee for backwards compatibility between nilfs2 versions. while it might be fine if you never upgrade, from kernel 2.6.37 on our kernels are packaged and upgradeable in ubuntu, nobody can guarantee that i.e. a switch to 3.0 wont break nilfs2 compatibility.

jffs2 is really old and obsolete, even if we would run our rootfs from NAND there is ubifs for such cases nowadays.