The best $5 I've ever spent...no, seriosuly.
I blasted my way through the campaign pretty quickly but there is a ton of replay value and different modes (survival and gun) that make this game such a bargain. Not to mention the buckets and buckets of blood and gore you spill along the way. Is there a story? No. Is there any dialogue? No. Is this game profound? No. Does it deliver an addictive good time that will make look at the clock and wonder where the last 2 hours went? Definitely yes.
Don't expect much going in and you will be very pleasently surprised. The one and only thing that I would change about this game is the campaign length, it was a little short. But no matter, you can mow through it again and again with different weapons and strategies each time.
For five bucks, you are cheating yourself if you do not buy this game.