So, er, you're suggesting that a good filesystem, what, calls sync() every
second? I can't see any way in which you could get the guarantees fsync()
does for files you really care about without paying some kind of price for
it in latency for those files.
And I don't really like the idea of calling sync() every second (or every
five, thank you ext3).
Being able to fsync() the important stuff *without* forcing everything
else to disk, like btrfs promises, seems very nice. Now my editor files
can be fsync()ed without also requiring me to wait for a few hundred Mb of
who-knows-what breadcrumb crud from FF to also be synced.