When you start this game, you will love it like I did. The graphics are flawless, the missions are varied, there are many cool collectables that you might search the whole level for.
The first problem comes at the end of the first level. It will switch to a diferent part of Springfield, not connected with the part in the first level. It means you have to learn the area again.
The second comes when you take control of Marge in the fourth level. It uses the same map as the first level but by this time you've half forgotten it. The missions feel repetitive and collecting the cool items is a chore. It feels like you are replaying the game from the start again.
Don't get me wrong, this is a four star game. The first three levels are awesome and alone earnt the bulk of the rating. But then you just don't really care if you finish the game.
My suggestion, go out and buy this game if you are a Simpsons fan and are interested in Grand Theft Auto. If not, Jak II or Jak III might be more what you are looking for. They have the gameplay this lacks.