Unfortunately, where this game is really lacking is the storey progression as there is no voice acting for the characters, its all put over by text and art frames without animation - which for a handheld console with the ability to play video files is very disappointing, however the game does make up for it with mini games. These can get annoying having to do them repetitively but is a nice addition.
Lets talk about the drug dealing feature... Theres an ongoing side quest that helps you generate more money which at the start of the game is very useful if your not one for using cheats. Basically, you buy the cheapest and resell for higher. The higher value the drug, the better the profit margin. It involves a lot of travel, although some dealers are very close buy in the city and once you've dealt with them before they will appear more clearly on your map which is helpful. The game helps you, marking which ones you should buy and lead you to a profit which arguably makes it too easy, but with every deal, there's always a chance there could be a bust!
The style of the world matches up to the PS2 games, GTAIII and the Stories series but with a more oriental focus in sound design. Another main difference being how the protagonist is animated. He appears a little more 2D as with the rest of the NPCs but it fits well. I find it to be a nice ode to the original GTA games on the PS1 too with the topdown view. It's very enjoyable. I don't usually play my PSP all that much these days but I've put a good few hours (3-4) in and it's certainly a game I want to play to at least story completion. Also, unlike GTAV it's actually fun to grind money. The shooting element and target locking is simplified but I think that is because of the top down style of this game.
Does it still hold up today? I'd say so. If you can pick this game up for the same sort of price, I wouldn't hesitate.