Andrew,
That would be unacceptable. The file system format won't change at all. I don't know what Simon has planned for the journal but I like how Solaris handles the journal. My limited understanding of it is:
On the server of the small society I work for, I've noted random crashes from time to time, without being able to get any useful trace messages. Setting /usr to read-only seems to fix the issue (the hard disk is brand new).
I wonder if this is not caused by SOFTDEPS. If it is the case, is it safe to disable the option from the kernel and go back to a "bare" filesystem?
Thanks, Vincent