Reviews can't do this game justice.
This game is packed with content, it will take you close to 50 hours just trying to atleast play once every challange and experience every track. If you are thinking about completing this game (collecting cars, gold medals in challanges, all tracks on S level), you might aswell book another lifetime.
Graphics, sound, racing, presentation - without flaw.
The only gripe could be lack of dedicated servers for multiplayer (ad-hoc only). But that's about it.
Gran Turismo PSP is what you'd expect from the series: definitive, polished, content packed racing game that has no equal on handhelds and can be compared to home console games.
If you can accept it's basic premise, it's handheld philosophy you are in for one hell of a ride!