Been playing this for about eight hours. I think I'm almost finished with the campaign. It's easily some of the most fun I've had in a while. It's not just a good game, but what Red Faction should have always been.
It has all of the awesome stuff from Guerrilla and then doubles it with all new awesome stuff, like the magnet gun, walkers, and a flying mission. Since it's linear, the path you progress down is specially designed (most of the time) to balance between kickass horde shooting and environmental destruction. Your main goal is usually to clear an area of enemies and how you do that is up to you. I found myself bringing their surroundings down upon them in creative ways before killing them all off and destroying whatever was left in an almost unhealthy fit of glee.