I have seen a lot of videos on LittleBigPlanet before, but this is absolutely absurd:
http://www.youtube.com/watch?v=ZiRgYBHoAoU
This designer basically made a functioning adding machine using nothing but the tools in LBP and his own creative mind.
People like Mrs. Wombat ask what the point of Little Big Planet is, and the best response to that I can think of is, "What's the point of playing with Legos?" They are really the same idea: to create interesting things using the simple, elemental tools given to you and your own imagination.
Like Legos, LBP can be used to make something that is just pretty to look at, something that is really fun to play, or something that is really a work of art and engineering rolled into one.
This isn't a game for everyone because of the gameplay mechanic and the complete lack of direction for the player, but that is what will make it successful, I believe. The game comes with a good number of premade levels that show what the gameplay and physics engine is capable of, but the magic lies in what users will be able to do.
I play almost nothing but sports games, so I won't pick this game up right away. But I do realize a brilliant game when I see it. In fact, Little Big Planet and The Orange Box are really the only two games I can think of that will make me deviate from playing the sports games that I do 99.9% of my gaming time.
Not everyone has to like it, because Wombat is right in that it isn't for everyone, but you have to give it up to Media Molecule for what they have created. The pre-made levels I'm sure will be varying degrees of fun, interesting, and challenging to play, but largely this game is as fun as you make it, and creative people like the guy in this video only make that clearer by the day.