Man, everyone is right on the money, the quality of this game increases so dramatically. The first areas were so simple, but the quality of these scenarios has increased greatly. This is truly a Halo quality game here.
My only complaints remains the disconnection I have with the theme. The atompshere is great, but it still doesn't have a certain "something". Halo's world, music, and design just really really appeals to me and this isn't on that same level. The game itself, though, is right up there. After seeing hoards of cloned enemies, I was surprised to see how much variety there is in the encounters. Each scenario is filled with a fantastic mix of enemies that forces you to approach them in a different way. Throw in stuff like those awesome mines and huge variations in the type of areas you are fighting in (which have an impact on gameplay), and you have something special.