I just picked up this game a few days ago and I have already put a good 10 hours into it.
I LOVE IT!
You can't tell the difference between the game and the show. Looks like you are playing in a live episode of South Park.
What I also love about it is that they have incorporated quests and items basically from Season 1 and on. So if you have watched pretty much every episode like me, you will have a really high appreciation for the game.
The gameplay is RPG. Everyone is in character just like the Black Friday episodes.
I don't want to give away too much, but I have already killed some exotic animals for Jimbo, began hunting for manbearpig, defeated the ginger kids and brought down an alien spaceship.
Even if you are not a South Park fan, you need to buy this game!