You wouldn't hear me talking about this game after 5 years.
The mindless killing is great, but...(continued in next section) and the graphics are fine and definately serve it's purpose. The gameplay is extended for a couple of hours with the multi-player, although it isn't that different from playing the single-player.
(continued from the first section)...after a few hours it all becomes VERY dull. You've seen all the enemies and gotten all the guns about half way through the game. Then what you get is just a bunch of rehashed enemies(different colour, different size(only one of them, The Head-less suicide guys, are remotely interesting) and the same lame guns for the rest of the game. Oh, yeah, the weapons are bad. They're all boring and unimaginative except for one: The Cannon. And, in the spirit of the game, I'll repeat myself and say: Unimaginative gameplay, enemies and weapons.
The Bottom Line
This game shows just how easy it is to impress gamers now a days, with a dull, mediocre FPS. It might just be worth your money because of the low price, but that shouldn't justify putting no imagination into it.
The only way for this game to live in the memories of gamers, is to keep pumping out sequels every year. And believe me, you don't want that to happen.
In short, a quickly-forgotten game, with a low price tag.