Technically, this movie is very good. The effects are well done, with very high quality computer graphics for a "Made for TV" movie, that won't stand behind theatrical release movies. The outdoor scenes were all well produced, placing the actors in a "real" discworld. The customs and environment are in a child-movie style, because of the story's background (it came from a series of books made for children). But that doesn't mean low quality. It just adds to the comical overall feeling of the film. The actors followed this same comical/child-oriented line when playing their roles.
About the story, it never gets boring, and a lot of things happen to the main characters. They practically cross the world in a single adventure, including a journey in "outer space". Multiple parallel plots also take place. In the end, this 3-hour movie entertains you the whole time. The main motivation is very original: following the steps of the first tourist. And the world description is ironically fun.
This story has 2 main perspectives. From the Twoflower point of view, it's a story about having an open mind. One may have much fun and learn a lot when he keeps his mind open to new experiences. From the Rincewood point of view, it shows that one must have persistence; and also that, even in the face of failure, your value doesn't diminish. You're not defined by your failures and/or successes as perceived by the others.
In the end this is a family movie, worth watching by itself, and even more with your children (if you happen to have any).