> Fast fsync() is of course welcome, but only really needed by some applications.
I know one: CouchDB. Beside the hype behind it right now, it's extreme robust append-only storage philosophy was enough to attract attention from the Google Chrome developers. In it's heart this algorithm relies on a fast and secure (as in not cheating) fsync().
CouchDB also has a nice user base, it's installed, used and run by default on Ubuntu 9.10
I guess other database systems also profit from a better fsync().