Well this piece of merchandise is worth it.
The gameplay is great. If you've ever played the original The Legend of Zelda or one of the Gameboy sequels, exploration is like that. The city of South Park is laid out in an intelligent way and all of the significant landmarks are present.
Combat is like Final Fantasy VI or any other turn-based RPG. You run into enemies on the map, a battle scene loads, and you and the enemy take turns entering attacks or commands. Attacking, defending, and using magic and special skills require various timed button presses, analog stick commands, and button mashing to maximize the effect. Smart way to keep the player engaged during fights rather than just having you enter commands and watch. You're joined by one buddy (who can be swapped out on the fly) who you control. The main cast of boys are the buddies, and you unlock each one as the game goes along. Each one has unique strengths and abilities (e.g. Kenny doesn't stay dead) that are handy in different situations or against specific enemies.
Your buddy follows you on the map screen as well, and occasionally makes funny quips or references to instances from the show. There are a lot of destructible objects and hidden collectibles all around, and it takes different skills and/or buddies to reach them all. You can talk to the people of South Park, and some will become your friend on Facebook. Facebook is your pause menu where you can see your status, items, skills, the map, etc. Its main screen is a wall where your buddies and friends from town post funny messages.
The leisurely pace and controls are great for sitting back on the couch. You can explore all you want or go from mission to mission. There are side quests, too, of course. The game certainly feels long, unless I'm just dawdling too much. I can't stress enough how much this is like playing the show. Don't let my comparisons to Final Fantasy or Zelda give you pause; the style of play and the source material are a perfect match. It should please all camps. RPG fans who don't watch the show will still enjoy the throwback gameplay, and fans of the show who aren't hardcore gamers can turn the difficulty down a notch and enjoy an extended episode.