There used to be a link on the home page, but now it seems to be in the USERCP.
Sometimes where there is a membership drive there can be freebies that come with the life membership. There were free holster certificates and Spyderco knives last time.
With each tier you do get more space for private messages.
Each tier gets progressively more.
With each you get the ability to have a larger than the normal 100x100 avatar.
You get the ability to start or be invited to join in some of the private forums.
There was supposed to be an @GlockTalk.com email address at some point.
Any pop up adds will be gone from your view.
You get to support a site that actually has operational costs.
As far as I know the @glocktalk email never came to fruition