If you had the choice to buy any PSP game you wanted, this is not worth it.
There are a quite a few pub games: darts, skittles, UK pool, US pool, and an arcade game. Another game is "Gang battle", a fun strategy based game that helps pass by time. There is one thing that separates this game from others: Game Sharing. I haven't tried it yet, but you can get your friend who has a PSP and play games together.
Now let me tell you about the problems with this game. The aiming system for shooting is a little hard to get used to. When you go into stealth mode, its not hard for someone to notice you. Your PSP will go flying across the room trying to pass these missions. The worst thing about this game is driving. Driving a car is hard and total rubbish. If you press on the handbrake, the car will make a 180 turn. The only cool thing is that it has an in-car view, but its not so useful in story mode.
My view on this game is to avoid it. If you want to experience London in your hands, rent the game. I am planning to sell this game and use the money to buy Grand Theft Auto: Vice City Stories. I think they should have just sticked with the original Getaway series gameplay. If they have done that, I may give this game a second chance.