a vig companion pass gets you a special swag bag that the vig's get. the bags contents usually range in price form $200-$300. In years past i know they have gotten things like a Full copy of Settlers of Catan, Arkham horror, THe DND 4.0 Monster Manual ,or some other games. They also gain access to early entry in the dealer hall, access to the VIG lounge , a special VIG will call/Event Registration, Complimentary Wifi and beverages, access to the VIG hotel rooms, and Full access to the lounge for all children ages 8 and under.
The swag bag may include a commemorative gen con t-shirt, Vig Badge holder, a VIG pin, Gen Con merchandise and promotional items from Exhibitors, Sponsors, Guests of Honor, Event Organizers's, etc., based on availability. There may also be VIG coupons, which could include discounts for specific booths in the Exhibit Hall and other special deals. Promotional items are not guaranteed, and swag will vary from year to year, based on availability
Here is the info page for it
http://www.gencon.com/2012/indy/cs/vig/default.aspx