I'm not really a Killzone Fan, but, let me say, that, for a PlayStation Vita Exclusive, it's really, REALLY good and VERY addicting. A game like this, is VERY HARD to not keep coming back to, even long after you've earned its Platinum Trophy.
***SPOILERS AHEAD***
Graphics: 5/5
Mercenary is a beautiful game and really takes full advantage, of the PlayStation Vita's hardware. This game right here, tech demo or not, is a true testament, to what the PlayStation Vita could do. Great job and rest in peace, Guerrilla Cambridge. You will be missed and thank you, for giving us this excellent PlayStation Vita Exclusive First-Person Shooter.
Story: 4.5/5
The Story takes place, during the events of Killzone 1, Liberation and Killzone 2. Plus, Intel clearly nods at these games, too and I appreciate it, even though I'm not really a Killzone Fan, despite having played all of them, but, haven't completed them all.
Anyway, you play as Arran Danner, a mercenary working for Phantom Talon Corps. A Mercenary Business, basically. Your main boss, is Anders Benoit, a real scumbag. He doesn't care about you, only about using mercenaries, for profit and halfway into the game, he does betray you. Also, you have to deal with two total psychos: one is a Female ISA Admiral, named Alex Grey and the other is a Male Helghast Colonel, named Vyktor Kratek. Both are after a virus, that a Helghast Scientist injected, into a Half Human, Half Helghast, 10-year-old boy, named Justus Harkin. Anyway, this is the main story and you end up killing 2/3 of these scumbags, destroy the virus and the game is over.
Anyway, I do love the ISA and Helghast sides of this story. It REALLY makes me wish, that more Killzone Games, were like this, instead of being one-sided only. Looking at you, Killzone 2, 3 and Shadow Fall.
Gameplay: 5/5
If you've played Killzone 3 or Shadow Fall, you'll be right at home, with Mercenary. Also, pretty much EVERYTHING you do, earns you money. It's very addicting and encourages multiple playthroughs and play styles. You can also unlock Special Abilities, through a Black Market Arms Dealer, named Blackjack, called VAN-Guards, which acts as Killstreaks/Perks. Not much else to say here.
Controls: 4.5/5
Controls are, for the most part, really good. Although, one minor complaint, is having to use the Touchscreen, to pickup Ammo, when you could, very easily, just push Triangle. Same with Melee. Having to use the Rear Touchpad, to zoom in and out, of sniper rifles, is a little gimmicky, but, it also works surprisingly well.
Replay Value: 5/5
In addition to Story, there are 3 Contracts you can play as well: Covert (Stealth), Demolition (Destroy Everything and Kill Everyone) and Precision (Objective-Specific, basically). All of these, on top of Multiplayer, which is one of the weaker aspects of this game, all adds tremendous amounts of Replay Value.
If you have a PlayStation Vita and are looking for a great Handheld FPS, you can't go wrong, with Killzone: Mercenary. Keep in mind, that the Story only clocks in, at around 4-5 hours, but, it's an enjoyable 4-5 hours, nonetheless. This game blows Black Ops: Declassified out of the water, with ease. If I enjoyed it, so will you. Take it from this 12-Year PSN Veteran. Killzone: Mercenary, is a HIGHLY RECOMMENDED, MUST OWN PlayStation Vita Game.
Final Score: 10/10