I saw this movie in the theater and it was an awesome experience. I just bought it on blu ray and it still holds up. It's cool to see the textures in such high quality and the audio commentary by Matt and Trey is worth getting it.
We all know what to expect from South Park, and the movie certainly delivers! Great fun, and you don't really need to have watched the show before. Cons: Kinda juvenile humor, certainly not for everyone.