Each time you run rsync over ssh, you are prompted for your password. You can make that go away as described at http://mah.everybody.org/docs/ssh. When I first tried this, it didn't work because of wrong permissions in /.ssh on the server, chmod -R go-rw /.ssh on the server fixed it. For each new machine, I only need to do the following two steps:
ssh-keygen -t dsa -f ~/.ssh/id_dsa -C "me@newmachine" cat ~/.ssh/id_dsa.pub | ssh me@server 'cat - >> ~/.ssh/authorized_keys'