Psychonauts is one of those few platformers were everything is pretty much perfect. The control scheme is simple, responsive and fluid, the in-game powers are useful and inventive, The characters are dynamic and engaging and the storyline is both immersive and entertaining.
Psychonauts is a truly great game, with only two glaring problems. Problem number one is that it is too easy. A lot of platformers are known for being notoriously difficult, but playing Psychonauts is like taking candy from a baby. With no arms. Problem number two is that it's too short. I don't know about anyone else, but I finished this game's story in under 10 hours. It'd probably take a lot longer trying to go for 100% completion, but after there's no story to see, some of the fun just isn't there anymore.
In short; Psychonauts is a great game. It's just too short and easy for it's own good.