It tells Harry how to get past the statue into the tunnel, by showing him a miniature version of himself. But in later books, there's at least one occasion on which the name shown on the Marauder's Map would not have corresponded with the person Harry could see a miniature version of... what's up with that?

It's also an astonishingly advanced and creative piece of magic. It's hard to imagine even Hermione in her seventh year making something like this. Then again, if you look at the schooling of Hogwarts students, there's not really much emphasis if any on being creative and inventing new things. Hermione is a brilliant student, but not necessarily very creative with spells like James and Sirius (and Snape, while we're at it) apparently are. I still don't know if I really buy it, though - Voldemort would kill to have a tool as powerful as the Marauder's Map, surely (sees through Polyjuice Potion, through invisibility cloaks including Harry's, and so on).