South™ Park™: The™ Stick™ of™ Truth™ (tm.)™ is one of the best licensed-property games I have ever played, though it's not without its faults.
Let's start with the good stuff. For fans of the show, it's hard to imagine a better use of the license. The designers didn't play it safe and crap out a generic game just to cash in. They took a great hook that was already built into the show (the kids of South Park™ live role-playing RPG-style) and ran with it. This is not a hard-core 100+ hour type of RPG, nor should it have been. Instead, it employs a more simplified style that requires timed button presses for attacks and defense. As a reference point, the gameplay is very similar to the "Mario & Luigi"™ RPGs. This is not only a very good thing, but it also perfectly serves the source material. So while the "RPG" aspects of the game are not particularly hardcore, there is just enough depth to keep it (mostly) interesting throughout. What really take the game to a higher level are the production values. The game itself looks and sounds exactly like the newer HD episodes of the series. Just about every character you could possibly care about makes an appearance, and they're all voiced and written exactly as you would expect. Absolutely no corners were cut in this department - the game really makes you feel as if you are in South Park™, interacting with its characters. The story is also exactly what you would expect out of South Park™. Although the basic premise is very simple - the boys fighting over an ordinary stick™ - the story ultimately progresses in ways you could never have imagined (or perhaps you can, if you've watched enough of the series over the years). The dialogue and voice acting are excellent, and there are plenty of laugh-out-loud moments from beginning to end. There are also tons of obscure references and cameos throughout, seemingly for no other purpose than to make the most hard-core fans chuckle. The whole game really is just a huge South Park™ love fest. In terms of difficulty, the default setting is fine, if a bit on the easy side. If you want more (or less) of a challenge, you can change the difficulty at any point, which is a great feature that should allow anyone to complete it if they put in the time.
Unfortunately, along with all of the things that make the game good, there are also a few low points. Several sections involve slightly complicated "quick time events" (not exactly in the traditional sense, but used here for lack of a better term). Setting aside the fact that these sections seem randomly out of place in an otherwise good game, the real issue is that they just aren't implemented well. The tutorials for each action are executed poorly, which can be frustrating if you don't pick up on what the game is asking you to do, exactly. Another low point comes towards the latter portion of the game, which involves a series of "fetch-quests". While I am sure the intent of this section was to lampoon this tired video game trope, they succeeded a little too much, as it started to get fairly tedious. It also didn't help that at this point in the game, I had already maxed out my character's level, so there was really nothing else to strive for, in an "RPG" sense. It would have been nice if there was no level cap, with enemies scaled to your strength (or something along those lines). Lastly, and this is just a pet peeve of mine, but apparently there are several collectibles that can be missed if you don't get them the first time through - just a warning to those who enjoy collecting things or 100%-ing games.
Overall, my annoyances with the game are fairly minor in comparison to all of the things I enjoyed. If you are a huge South Park™ fan, I think this is a no-brainer. The amount of care that went into making it is readily apparent, and worthy of your money (at least, now that it's only $40 - the original $60 price point was way too much). In terms of length, it's hard for me to estimate, but I would say it will probably take you anywhere from 11-18 hours, depending on how deliberate/OCD you are. It's really hard for me to imagine a South Park™ game ever being done better than this. Needless to say, non-fans should stay away. But for anyone else (assuming you can get into the simple RPG gameplay), it's definitely worth checking out at some point.