I always viewed Vince as just the medium in which E, Turtle, Ari, and Drama's lives cross. This is the first time anything really interesting has happened to him. usually its "go film a movie and f**k some randoms." he's kinda like michael scott on the office... yeah he's kind of the "main character" figure but the story really revolves around the other guys, like jim and pam.
Vince is the exact opposite of Michael. Watch what happens to the Office after Steve Carrell leaves this season. Sh*t is over. Now say Vince is off shooting some movie that the cameras can't follow him to, Entourage could still go on, pretty easy
Vince is like that wack a.ss dude on how I met your mother.
[pic - click to view]
He is the main character but you'd never even know it