Using RSYNC for replication?

A sequence of events ocurred to me today that left me wondering if I can
rsync the raw files as a form of replication. I'd like to keep
postmaster running, but flush and lock everything, then perform the copy
  via rsync so only the new data is propigated, all while postmaster is
running.

In general, data is only added to a few tables in the database, with
updates occuring infrequently to the rest. Rarely are deletes ever done.
   During the sync neither DB will change except as part of the rsync.

I think this would be a quick, dirty, safe and efficient way to
accomplish this without having to take down postmaster and send the
whole shebang over.

Are people using this? Will it work? Is it feasible? Thoughts?

Many thanks in advance,
-Jason