This is a very fun game to play. I agree with a previous reviewer that it is centred around teamwork (though you can go solo if you prefer). One point to clear up first of all is that once your preliminary 50 hours game time runs out, you need to pay for realtime world points which you can then exchange for game time. To get 30 days unlimited access, it costs 7.99.
Pros include; a great social area where you can customise appearance, clothes, tattoos, cars etc. It even has a facility where you create a basic tune that your opponent hears once you've killed them (I can't count the number of times I've heard beverley hills cop when I've died!). You can import you're own music collection to the game, but please note it has to be saved in the MP3 format, in other words you cannot import directly from the standard i-tunes format. If you play a song in your car which other passenger do not have, last.fm streams a similar song to them so that they can hear the same genre.
Cons; graphics are not great, but decent enough for an MMO game. Police enforcer stun guns are quite irritating as you will be stunned for a considerable length of time. Intermittent problems with the servers have caused lots of people to get kicked out of the game when trying to change lobbies or even alter appearances. As previously mentioned by someone else, you do have to play through for quite a while to unlock things. After 10 hours of play I have unlocked very little, but then again that's all part of the challenge.
One final important point is that if you intend to play this game with friends, then keep in mind that once you have selected your game world/server, you can never change this! You need to make sure that your friends all select the same server and faction (criminals or enforcers) at the beginning.
Hope this review helps and doesn't put you off. For it's faults, it is a very enjoyable game once you land in a steady group of players.