If memory serves - which these days is questionable - P.M. costs around $50. He gives info about rides and attractions, but more than that he tells lots of stupid jokes. He also has some games programmed into him that you can play. He'll tell the jokes and play the games away from the parks, too.
As for attraction information, he's supposed to tell you wait times, etc. I remember when we were in line for Splash Mountain he gave a warning that he should be put away so as not to get wet - not good for electronics you know.
When you walk into the park his programming is supposed to be updated with latest information. Just be sure you have fresh batteries in him or you may think he's broken. (That happened to us on our last trip and we spent about 20-30 minutes in one of the stores trying to get him working right.)