So how do you keep track of who's ahead then--do you like acquire cards or something?
Oh, yeah... each player's cards are arranged on the table in what's called a "power structure", starting with their Illuminati. The Illuminati and each Group have one or more outward-pointing "control arrows", which indicate how many Groups each can control. So everyone can see what Groups each player has, and how close they are to winning. Plot cards stay hidden though... so you never know when a player may reveal a hidden Plot for a sudden win.
See here for a sample of some INWO cards.