You know what has me excited? The fact that there is a DLC link on the title screen (at least on PC). I am a huge fan of games that provide me reasons to return to them (aka Borderlands 2), and I can see some long legs on the future of this title if they regularly provide 1-off stories or even collections of side quests that are specific to a particular episode/series of episodes.
The reason I think this would be particularly successful in South Park's case, is that they have already created mini worlds regularly that each have a detailed and self-referential story. Off the top of my head, I would gladly drop $10 for episodes like Imaginationland, Console Wars, Christmas, the Coon, or anything in Canada. I can't help but wonder if that's the direction Jordan Thomas (aka the Bioshock 2 creative guy) (aka the design consultant for SoT who was pulled in after THQ bit the dust) is down this long-legged rabbit hole.
PSA, beware the RESET button! It does not simply reset your progress in the area/quest you are in, it resets your game! Good for getting great boss drops, but it takes away all of your warp-points and such, as if you were starting from square 1.