Postal 2 is obviously known for it's extreme amounts of violence and dark humor. This game is obviously not for everyone, but it's a fairly decent game.
The game is organized by "days" and lasts a week (factoring in the expansion). Each day, the Postal Dude has a list of errands to run. The errands range from picking up milk to paying a ticket, and almost always go horribly wrong. This is where the game suffers alot, the errands feel completely repetitive. As the end result is almost always the same - a shootout. Add in the constant load times between levels and the game gets dull fast. It's just running through fairly unorganized areas to get to another area then another area, just to go visit a church, then you confess, and then you shoot your way home.
Fortunately the game is fairly open ended, and allows you to just about do anything (limited of course because of the lack of fast travel or cars). The weapon selection is pretty good, with lots of FPS staples and quirky weapons such as a pair of scissors or a diseased cow head. But soon the mindless killing gets boring fast, the A.I. is decent, but it gets stuck and does some idiotic things sometimes but this game doesn't need super smart A.I.
If you aren't easily offended and want to kill a couple of hours definately check out Postal 2. There isn't much replay value, but it'll keep you entertained for quite some time.