I typically like South Park's modern episodes and I thought Stick of Truth might be like them but instead it relies a lot on the crude humor and in-jokes of South Park which are kind of the weakest part of the show.
The combat system is decent enough and the base of the game is structured like a typical RPG. But, that's one of my problems... it's just typical. It doesn't do a lot to break genre conventions or add something new to the game. The only unique thing about it is that it has a South Park skin slapped on top of it.
And that's just not enough for me right now. Maybe some day I'll come back to this game but not right now. That being said, if you're a huge fan of South Park I bet you would really like this game. If you're more of a casual viewer like me... not so much.