Interesting take on killzone, the only one who is not an fps, its first half is not a huge challenge, the second one is .... inconsistent, the boss fights are a huge pain, they are accurate with nearly zero cool downs to their attacks, it does not help that the controls and auto aim were made for the slower rhythm combat in the first half.
you need to download the 5th chapter dlc if you want to see the real ending of the game leading to killzone 2, look for it on google it was free and easy to install.
i wouldn't call it an essential play, but an entertaining distraction. 6/10