Klei Entertainment told Joystiq that following its official launch, the game will receive six months of free content. The game is influenced by Minecraft, which has benefited greatly from a constant stream of updates, so it makes sense to keep players engaged with shiny new things.
We've seen plenty of the game's main character, Wilson, but other unlockable characters will have special abilities. Willow, a girl who can light her own fires, was shown at PAX East.
Klei has already been creating additional content in closed beta, as it has offered extra content semiweekly. You can pre-order at a lower price, and get beta access to boot. Or, you could try out a free timed demo on Chrome.