The help for LOGIN/NOLOGIN at
http://www.postgresql.org/docs/9.1/static/sql-createrole.html: "...NOLOGIN is the default, except when CREATE ROLE is invoked through its alternative spelling CREATE USER." The help for CREATE USER: "These clauses are an obsolete, but still accepted, spelling of SUPERUSER and NOSUPERUSER. Note that they are not equivalent to CREATEROLE as one might naively expect!" Eh?