How does it stack up to the rest of the Halo series?

Very simple gameplay. The AI isn't very complicated and it has absolutely no survival instinct. They will just stand still taking hits until they can't see their target. Then they reposition until they regain line of sight. They don't take cover or use grenades. The enemies are very spongy after a certain point. After that certain point, weapon variety goes out the window in favour of having what is basically the same gun but with small differences in dps and ammo efficiency. You basically get a bunch of functionally identical automatic rifles, a guided missile launcher and a sniper rifle at the end of the game. For some reason there is no phased plasma version of the shotgun so that play style is not served in the second half of the game.

Player movement is very slow. Because of that, stealth sections overstay their welcome. If the crouched movement was the same speed as standing speed, this wouldn't be an issue. The weapon animations are alright. Some of them are slow and stiff but you get used to it.