This is a fantastic game especially for one that was created all the way back in 2006. You forget that it is 10 years old when you are playing; this is mainly due to the fact that it is a concept that is currently unrivalled when compared to games of today.
Admittedly, it takes a fair amount of effort to create a multiplayer game; the server has to be hosted by a member of your party as there are no public servers available (This requires forwarding of port 27105). Other than that, it's an easy game to get into.
The basic premise of the game is that you have to hunt for your quarry, while being hunted. You get a list of the best priced weapons when pressing M, if you find these and kill your quarry without being detected and therefore detained, you will get a higher amount of money.
There are various maps, all of which are fairly good, these can be selected with console commands. The spare slots in the server are populated with a fairly good AI.
If I can offer one piece of advice, it's keep an eye on the people around you, and watch that eye.
My only complaint is that this game is so old, if it was revamped and brought into today's standards; I could imagine an even greater game would be born.