A joke about the heavy founder of Valve, Gabe Newell, a game developer that creates great games but is terribly slow. (See Valve Time) It stems from Gabe himself saying that a certain game will be "Worth the wait" when it comes out.
It created a Youtube craze, just look it up on there.
Person 1: Half-Life 3 is taking an awfully long time to be released, and Gabe has no news...
Person 2: Hopefully it will be worth the weight!