CountChocula
Keeper of the Watch
They're trying to keep it fair (seemingly) by shuffling the ones on the front page. Some stayed there quite a while though and got much higher visit counts than others. I suspect outside traffic is factored in to determine how high up your entry goes. That would make the whole greenlight idea lead to the exact same results as previously, basing inclusion mostly on existing popularity, which is probably exactly what they want.
I think it will work the way the workshop currently works, with the additional filter of excluding the projects you've already rated by default.
In a couple of weeks after launch, if you navigate to the main page, it will likely show the most popular (most thumbs up ratings) projects of the week by default (not the most popular projects of all time), and it will exclude any projects you've already rated.