Gone are licenses and long marathon races; most of the game is a pick-up-and-play experience, trading out long races and licensing for quick races and tutorials that give credits that can be redeemed for, you guessed it, more cars. There are 800 cars in the game and each has its own unique feel of power and control. The higher end cars have the power and speed and it translates well, even without vibration, while the lower end cars show that there is something better to be had.
The controls are sort of a sticky point, and when using a manual transmission, you basically have to use the D-Pad in order to easily shift when it is much easier to use the analog stick to steer. The controls, however, are very responsive and the car turns when I want it to turn, goes when I want it to go and brakes when I want it to brake. The controls could be helped with a larger analog stick (think DualShock size) but if I wanted to play it on something like that, then I could easily play Gran Turismo on the PS3 or 2.
Gran Turismo is known for its ultra-realism, and while it gets rid of many staples of past Gran Turismos, it is the most realistic driving game on the PSP. It provides a good pick-up-and-play experience but also provides enough depth for a 5-6 hour play session.
If you're looking for a realistic driving experience, definitely pick up Gran Turismo, while it's not as in-depth as its console big brothers, it is one of the best driving experiences you will find on any handheld.
Gran Turismo is available for the PSP via PSN and UMD.