I have to say one thing before i get started, this is an amazing achievment, it makes you think of a portable like a console. Now, to say this is an good game is an understatement, its fantastic. Imagine if you can a whole city in the palm of your hands. You can controll whether citizens live or die. sounds good doesn't it.
Grapics are amazing, slightly better than the ps2 version of GTAIII. i say only the ps2 versions, because on the pc you can alter the resolution, and make it look a whole lot sharper. I also have not played the xbox version.
The audio is a let down for me, because i like alternate music, which this game featured none of. The only station that sounds realy acurate is the rap station, which has a good number of tracks. Like gamespot said, you will find them looping more often than you would like, presumaly due to storage limitations.
The missions are fun, while they last. The main story missins only last 12 hours, if that. That will leave you around the 45% mark if you did nothing else. There is all the old minigames (with the exeption of house robbery) form the old ones, wiht new ones added in, like avenging angels, see the sights before you flight and others. they add some depth to the game, and are generally quite fun.
Then there is the newest addition of multiplayer. This consits of seven different games, supports 6 players, and creates the whole grand theft auto universe for you can up to 5 friends. this is a fun addition, but again your friends have to have a psp and another copy of the game.
There is also the addition of custom tracks, which means you can add your own songs instead of listening to the radio. It seems like a good addition at first, but you will soon come to realise that your collections of mp3's are usless and songs need to be ripped from a store bought cd.
All in all i will still give this game 10/10. because of its sheer sise, replayability and its limitless fun. Buy a car charger and take with you on long trips.