Bloodbath to say the least.
I got to the point where I already got everything you can buy and was just sitting there with 5k health and building health and the "jackhammer" auto shotgun (personal favorite) and just hosing them down every 3 secs. its a very fun game up until that point then it kinda starts to plateau. not really that hard of a game but a good frustration relief, probably wont play it again sence you can pretty much destroy it in one sitting.
Give it a 9 for peaking out instead of making it impossible.
But a 5 for being so damn violent and amazing.