I'm not sure of any reason to not give the user account a password (on this platform). ... I also recommend assigning a strong root password, to help insulate against generic userland exploits. If the passwordless method described is chosen, the user MUST disable password authentication in /etc/ssh/sshd_config (or anyone connecting will be granted shell access (and presumably, soon thereafter, root)).
I recommend the following settings, regardless: PermitRootLogin no PasswordAuthentication no