We currently don't have a premium system at the moment. We had one but it was part of ZAMs but when we split off from them we shut it down and those who had premium continue to have it.
As for what it would entail (or at least used to) is an ad-free experience across the site and a badge below your avatar. It would be like you using an ad-blocker but still supporting your favorite addon site to help keep it open.
__________________
"You'd be surprised how many people violate this simple principle every day of their lives and try to fit square pegs into round holes, ignoring the clear reality that Things Are As They Are." -Benjamin Hoff, The Tao of Pooh