The major benefit is a larger PM box. It gets larger the higher the membership.
You get the bigger avatar, an option of starting a forum here for other paid members with you as a mod, or the ability to join under invite other private forums.
An enlightened zeal for the energy and efficiency of government will be stigmatized as the offspring of a temper fond of despotic power and hostile to the principles of liberty.
Alexander Hamilton, author of Federalist No. 1. 10/27/1787