I wonder if this could be used as a replacement for Vagrant's rsync feature.[1]

From Vagrant's documentation:

  Vagrant can use rsync as a mechanism to sync a folder to the
  guest machine. This synced folder type is useful primarily in
  situations where other synced folder mechanisms are not
  available, such as when NFS or VirtualBox shared folders aren't
  available in the guest machine.

  The rsync synced folder does a one-time one-way sync from the
  machine running to the machine being started by Vagrant.

The disadvantage of the above is that it's a one-time, one-way sync. SFS would overcome this limitation, if I'm not mistaken.

[1] http://docs.vagrantup.com/v2/synced-folders/rsync.html