Pain in the ass difficultiy increase rate...
After you destry the chooper, the game get STUPIDLY harder....they enemies weapons begin to be able to kill you in 5-10 shots or 3-5 shots if they are in a group.
In one area, the RESPAWN FOR EVER, I had almost no ammo, it was hadr to se other weapons thay HAD been dropped on the floor, because of the sheels and dead bodies. What ever happened to the counters on the wall telling you how many kills you needed to get into the next room?! I had killed over 100+ enemies an the dam door didnt even open (Thhus, I ended up dieing and quit the game after im 15+ try....-_-)
Some weapons were WAY to small to see after blood and bodies had slattered themselves all over the place...making it harder to switch....
I had to resort to tricking the poorly programed bots to mass pile up near me so I could club them all (after to in that group died, 5 more would spawn....never ending....), and I had to do this on MANY other levels in the game....so on top of poor bot AI (Jump when I jump, try to go where I go! =D....idiots), the games weapons and level design were bad.
The only good thing this games HAS is updated graphics....nothing more.