There's a massive amount of gameplay in the Killzone 3 dev diary posted below, so fans of the series should definitely scope it out. However, fans of not seeing dudes get their faces, necks, eyes and chests absolutely ruined by knives might want to go look for slightly friendlier videos.
Visari is gone, but the war is far from over. Helghast forces have mounted a devastating counter-attack, prompting the ISA evacuation of planet Helghan. As new Helghast battalions appear with more powerful weapons, ISA forces find themselves outmanned, outgunned and surrounded.